some exhaust rear muffler companies claim to increase HP by 10-12%. is that for real? is this including the exhaust pipe?


http://www.2kracing.com/maxima-exhaust/

 

it could on certain applications like a TOYOTA SUPRA which is twin turbocharged. My cousin gained 38whp on his 97 supra tt just from an HKS catback. but on a Maxima, forget it. You'll get like 10whp at most with a catback. The ypipe does the trick. The 2 combined can be pretty good.