im about to order the jdm dc header for my gsr. do i absolutly need to buy the gasket and flange to bolt this header up? i was planning on bringing it to a muffler shop and have it put in custom w/ a cat/ test pipe. any help please!

 

The flange no, but the donut gasket you should...just because its a b*tch to find it elsewhere (and you need it).

 

you will need a 2.5" flange on the test pipe or cat you install. the factory 2.25 will not work. The donut gasket is available from honda for 25$. ask for the S2000 donut gasket, it fits perfectly and is high quality.