According to Soul, their catless headers + valved exhaust is worth 9 RWHP. I have their catted headers / valved exhaust setup though fortunately, the previous owner spent the money and not me (wasn't worth a dime in resale, so all good for me). Absolutely not worth the $8500 shipped they want now for this setup, especially since it is just a stainless steel setup. I get Porsche tax but I was paying Vette tax previously and nothing close to these prices for exhaust parts.I would think that my Soul long tube race catless headers and a Milltec muffler is more like 15 HP. The Softronic flash, race 78 mm throttle body and Plenum certainly pulls it all together nicely. I would guesstimate is about 308HP @ 6700 rpm at the wheels. I did this to improve the flat spot in torque around 4500, which it certainly did. I have had no problems with this system in 4 years of use.
What does it dyno? Seat of pants, sales pitches, etc. don't mean as much as a good before and after SAE adjusted run on the same dyno. My bet is that cork wasn't all that big...I run headers and muffler without cats. The car sounds mean and has really come alive. Now, I have also improved the intake side with IPD, GT3 goodies along with a tune. These cars came corked from the factory because the little ol' Cayman cannot out perform the 911. If you have the coin I highly recommend opening the car up to see the full potential.
No, a dyno of your car, not a sales-pitch dyno by someone that HIGHLY benefits from inflated numbers. Very different and it is incredibly easy to manipulate dyno numbers.
Here's a dyno sheet with cat back exhaust. Imagine headers. I'm no wine connoisseur but you can be the judge on the size of this "cork". My car has come alive and my Porsche tech was pleasantly surprised on how the car performed. To each their own.