are there any difference? does a itr b bipe bolt right onto a gsr perfectly or do you have to mod it a lil to make it fit

 

IIRC, the GSR b-pipe has a 1.86" OD, while the ITR has a 2.25", that bottlenecks down to 2" at the flanges.

If you have a 94-99 GSR, you'll need to add ~ 4.5" to the b-pipe. If you have a 00-01 GSR, it will be a direct fit.

 

cool thanks