Originally Posted by kitw
On an NA application, secondary cats vs Akrapovic Evo vs catless, I had a total horsepower variance of less than 9 horsepower. I'm happy to give up 2% power to not stink as badly.
I would have estimated 5-10 rwhp for the secondary cats and 10-15 rwhp for the primary cats, so your results seem right to me. Were I trying to maximize power, though, I would want all of potential gain, not two thirds of it. The small gains may not seem like much, but they all add up.