have you checked out some of the sentra forums. check out www.b15sentra.net and www.thevboard.com. Also check www.qr25de.com(net) not sure which one, too lazy to check.

if you can't find anything on those, check out the following shop, don't know anything about it, just one of the forums recommended it. I know they carry Hotshot stuff, thats atleast a good sign.

http://www.balancedperformance.com/

Good luck man, let me know what you find out. The SE-R has the same motor = similar tuning.