If I get 2.5 piping for my new exhaust system (s-pipe back), the increase in size wont do anything unless I replace s-pipe and the header right? So I should really get a new s-pipe and header?

 

It will do something. I just changed my exhaust to the Megan Racing 2.5 inch s- pipe back exhaust and I felt an increase right away. The car even pulls harder in the higher rpms. It was definately worth the money.

 

if you do a cat back ( i assume that is what you are talking about, because if you did a s-pipe back, that would be an s-pipe back exhaust) you will get an increase in power, but not as much as with a header and s-pipe.

reasons:

air flow is more restricted in the stock header and s-pipe, but once it gets to a pipe that is wider and has less bumps, it will be easier for that air to complete its path, there for an increase in hp

 

you will see a drastic differance when you add a header and s-pipe though

 

Im talking about draxas s-pipe back exhaust.

 

draxas is a very good company, and you will see very good gains with that exhaust. once you add a header to finish the exhaust, you can expect around a 10whp gain or more

 

i have headers, and s-pipe back exhaust..the biggest difference came from the headers and s-pipe the catback wasnt that big of a deal...i actually lost some lowend when i did the catback and gained some top...i lost to an rsx-s by 1 car length...the difference was nice.

 

Cool, get a pulley and try again and if you dont yet have an intake... definitely get one of those!