which header to use in a eg with b-series engine? also that will bolt up to stock exhaust pipe location. i've heard the gsr pipe is longer than the ls, or does it matter? will modification still need to be done to the exhaust pipe. i am running 2.25 at the moment.

 

It depends on what motor you have.
I have a 93 si w/ gsr motor. B16 headers are too long,
gsr are too short. install headers, take your car to a muffler shop.
$30 later, no more headaches.