It seems to me that there is only one way to gain HP with aftermarket exhausts, and that is to convert to single exit. Are there any aftermarket dual exhausts that gain any significant HP numbers? I don't want to spend several hundred $$ and get 2 hp gains. I know that these units may be lighter, but is the small HP gain and lighter weight really worth it? I don't want to convert to single. Would just getting strait through mufflers do the same as any aftermarket dual system, except for the weight savings? On top of that, is the stock exhaust 2.5 or 2.3 inches?

 

single is good for me.....I got Apexi N1 single

 

This car is very much maxed out from the factory in all respects. No exhaust will give you substantial horsepower gains, the best single outlet exhausts give 5-6H.P. if that. Choose for looks and sound primarily. You could always just change the mufflers and save a few bucks and some weight.