what do i need to install my dc jdm 4-1 headers, so the 2.5 inch collector fits up right. TIA

 

you'll need a 2.5" carsound cat with a 2.5" to 2.25" flange to connect to your stock exhaust.

 

Perfectly said!!

 

You do NOT need the 2.5" to c.25" flange. I would recommend that you get the 2.5" cat (2.5" inlet and outlet) from SMSP. It will fit perfectly as the 3 bolt flange is a perfect match to the stock flange on the b-pipe. In the future, if you upgrade to a 2.5" b-pipe, you would not have to re-flange the cat.

 

what if im gonna be installing a apex n1 exhaust???? help plz