Quote Originally Posted by bennjamin View Post
2.5 is too big for a "dc2" (assuming its a vtir with the usual mods....) full stop.


IF you have heavy work , or supercharged etc 2.5 is great. But the usual intake/header mods do not justify a larger than say 2.25inch system

Noted that the cat-back piping should match the outlet size of the cat itself - which should also match the collector size of the header too.

IMO if it must be a 2.5 inch , use a standard ITR muffler or similar to tighten the sound and aid throttle response both down low and mid range. Back pressure is real and is needed on smaller engines.
i on my D15b7 have ebay 4-2-1 headers, magnaflow cat and 2.5" stainless catback with one resonator and an xforce 2.5" s12 twinloop
runs great - i was a true beleiver of the whole 2.25 over 2.5 for n/a honda - but after i got that system put on the car i was like ... eh almost no difference between that and 2.25
the header collector size is still the same - it than bottlenecks OUT to the cat after a bit of piping - perhaps this is why