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Fabspeed was very helpful in helping get the problem properly diagnosed - they directed me (us) to a local dealer of theirs and arranged for the diagnosis. This very same issue (this same code, loose and or missing bolts) has shown up for several posters us here, and Dr. Phil & I went thru this with Fabspeed at the same time. I had multiple discussions w/ Fabspeed during the diagnosis and have subsequently suggested to them that they stop sending those composite gaskets and specifically direct the use of only the OE gaskets. You should call them to see what they are now saying about this issue & regardless, if they show up with the composite gaskets, throw them away (the gaskets, not the headers :hilarious:).

Their headers (I have the catted "sport" version) are truly a GREAT addition to the car. They just sort of "wake up" the engine. Much improved in the RPM range of the infamous "torque dip", better midrange torque, and a truly transforming improvement to sound. I believe this is generally felt to be the best first mod to the GTS / GT4 platform. I also understand that a pro-tune further optimizes the header installation, but I haven't done that yet.

If I had it to do all over, the header installation would still be the #1 mod, just use the OE gaskets and rigorously follow the bolt torqueing sequence.
Thank you GC/540gone. So there is no tune involved, just swapping out the headers? Fabspeed claims 26WHP increase, and more impressive 39ft/lbs at 3600 RPM - would you say that seems about right in the real world? If so, it does indeed seem like a bargain for $3k. While I own a 4 post lift, I'm not sure I have the cajones to try this myself. I would picture Preuninger over my shoulder saying, "Dummkopf, you must loosen dieser fahstener before zat fahstener, andt only with a Stahlwille J1567DZ torque wrench set at exactly 17.75426 Newton-meters."
 

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So there is no tune involved, just swapping out the headers? Fabspeed claims 26WHP increase, and more impressive 39ft/lbs at 3600 RPM - would you say that seems about right in the real world? While I own a 4 post lift, I'm not sure I have the cajones to try this myself.
Correct, no tune involved. You also may want to think about warranty issues. I had a conversation with my dealer and they seem reasonable. That is for example, if the transmission falls out, they are not going to deny a warranty claim due to the headers. If the engine seizes they will not deny that claim if you have after-market suspension components. You get the idea. Actually, I believe Porsche HQ makes the call on some, if not all, warranty issues, but it seems the system is reasonable.

You can get a tune with or without headers, but I believe the tune gives more impact if, with headers, you also get a larger intake plenum (from 74 mm to 82 mm, or maybe vice versa on the 2 and 4). Thus, you can allow more air through the engine and then add the tune to take advantage of it. I am guessing issues like a bent a rod, valves, or broken piston fall into the no warranty coverage in this scenario. They may be more restrictive on allowing warranty claims based on over-revs as well if you've done a lot to the engine. A lot depends on your local people it seems too, and how they present the case to Porsche.

Regarding the install, if you have a lift you gotta do this yourself! I have a 2-post lift, and it was really easy. You can download the document I put out on P9 to see the steps. The headers only have 9 bolts and they are easily accessible from underneath. If you remove the back two tires, the 2 bolts that connect the headers to the exhaust are easy to reach. That's it: 9+2=11 bolts per side and you have to remove and re-install the O2 sensors. Reaching a couple of the bolts for reassembly requires a small socket and angle connector, but that is about the only "trick" to it.

I'll make a deal with you...tell me when you get the headers and want to do the install, and I'll give you my phone number and you can call in help if you get in a bind (phone a friend type of thing). If you don't have time, I understand taking it to someone, but don't not do it because you think it might be complicated! :)
 

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Discussion Starter #23
Just a note to the poster who asked why Fabspeed was shipping the headers with the composite gasket: There are many (possibly hundreds) of installs using the composite gasket that are working just fine. The problem Bob and I both experienced was that once the bolts get loose, the gasket is compromised, and simply retorquing the bolts doesn't solve the problem of leaks. This can happen if the initial installation does not torque the bolts down in the right sequence, and using the right (two-stage) procedure. It doesn't always happen, but when the bolts loosen, and some fall out, the only solution is a new OEM gasket and the proper installation procedure.
 

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When I bought Fabspeed GT4 Sport headers last year, the gasket was cut so close to the size of the exhaust port opening on the heads that any mis-alignment of the gasket would block flow. Normally I like the gasket to be a close fit. To do it right, you'd need to put a video borescope into the O2 sensor hole to verify that the gasket was aligned with the head port opening correctly and then once correct, tighten the bolts. The factory steel gasket has a much larger opening so that any movement of the gasket, limited by the bolts and bolt hole openings in the gasket, will not block exhaust flow no matter what position the factory gasket winds up at..

V6
 

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I'm having the same exact issue after an April install of Fabspeed headers. 540gone, I just sent you a PM.


I have an Accessport, do you know if there is any metric to monitor or log to better uncover if the gasket could be the issue?
 

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I'm having the same exact issue ... do you know if there is any metric to monitor or log to better uncover if the gasket could be the issue?
darcus-->there are some very experienced folks that feel certain the gasket is the issue, based on extensive troubleshooting. I replaced mine and all has been good since...have you checked your bolts?
 
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darcus-->there are some very experienced folks that feel certain the gasket is the issue, based on extensive troubleshooting. I replaced mine and all has been good since...have you checked your bolts?
I just called Fabspeed and they said that they are quite confident that that is the issue and are actually ordering new gaskets now and will get me on the calendar to fix it for me. Glad I found this thread!
 
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Just note that any leaks in the gasket can cause air to be drawn into the exhaust. The front O2 sensor will see the extra oxygen and the DME willl enrichen the fuel mixture to get what it thinks is a proper O2 reading. This excess fuel does not get completely converted, causing the after cat O2 sensor to read too much fuel, generating the P2099 code.

If the leak is fixed quickly, it is likely that no damage will be done.

V6
 

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I have been waiting for the inevitable challenge to the 'exhaust gasket leak causes air to get into the exhaust' statement.

First, the exhaust exiting each cylinder is a pulse. It is a pressure wave. Since there is valve overlap, there will be a small period of each revolution where there is a negative pressure. This alone can cause some air to be pulled by the gasket into the exhaust. A second cause, and perhaps stronger one, is that the aftermarket headers try for equal length tubes from the flange to the collector. As each exhaust pulse passes through the collector, it also creates a vacuum on the other two tubes. This vacuum has the purpose, in a non-leaking exhaust, of helping pull the next exhaust pulse from another tube. This increases horsepower over a design-set RPM range. Short tube headers increase higher RPM horsepower and long tube headers help increase lower RPM horsepower. This is similar in reason for flapper valves in the X51 intake manifold to vary length of the intake runners, which also optimizes horsepower over different RPM ranges.

The combination of these two vacuum-generating behaviors lets air into the exhaust via a leaky gasket, ahead of the first O2 sensor, altering its reading to appear too lean.

V6
 
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