Considering the same diameter, for cat back exhasut are some giving higher whp gains then others? because on the ARk site that dts exhasut is estimated 15 whp thats seems an awful lot, no? Or are they all at about the same?

 

well they have dyno to prove it.....none the less......GMPP has a dyno'd gain for 12hp....
so yeah knowing ARK 15 hp seems pretty reasonable!
any mendrel systems of 2.5" should give you gains from 8-15 hp with other minor mods eg. intake

[edit] oh since ur in the 2.2L forum....ur gains might be halved....