Put a super trap diffuser on the end of the spec exhaust for a customer to meet a sound level. He complained the car was down on power after the weekend so we took it to the dyno. The diffuser robbed 19 hp from the car. Bad idea.
Surprising. How many plates did you use? I put one on and while I noticed a power difference, I doubt it was that high. The bigger problem was how far it stuck out.
I put all that came with it.