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."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.