My buddy has a DC Header made for a GSR. He wasn't to put it on a LS but it's a few inches to short. He wants to get a resonator instead of a CAT. Does he buy a resonator for a GSR or what does he have to do?

 

stick with the stock exhaust. DC is not really a 'performance' header.

 

He needs to simply have the piping extended from the collector to the stock cat. Sounds like he has a 94-97 GSR header, which is shorter than the other stock Integra exhaust manifolds.

Do not remove the cat. We all breathe the air. Even my smog exempt car has a cat. A good one doesn't cost any horsepower.