nos is ok...
you cant run it for too long, as long as exhaust temps dont get above 1200 you should be ok...
no residue probs or anything...
it is all good...
go to
www.rodmillenstore.com
they have tuning stuff for the gs400
it is sweet shit there...
but nitrous is ok... as long as you dont lean it out... use a zex style kit that keeps the a/f ratio close to stock, or use a wet setup like nitrous works that adds fuel along with nitrous... this ensures that it wont lean out...
both kits are 509... and i sell em both, so i know they work... check em out...