i have a 91 integra ls and i bought a header through the internet and they sent me a 94+ integra ls header. is there any way i can install it? my catalytic coverter is farther than the 94+ integra.

 

Its pretty straight forward... http://www.c-speedracing.com/howto/header/header.html
But I don't know if there is going to be any modification required at the collector end.

 

depends what kind it is. Some headers that fit a 94+ will not fit a 90-93 because there is more clearance for the down pipe on newer integras. If thats not an issue, you will need to get the b-pipe resized. I would return it.