i have recently put a few mods on my 2004 s/c xterra, i put on the K&N air intake, and i also put on a smaler pulley, the stock pulley is 2.6" and the one i put on is now 2.35" I can totally feel the difference, im estimating that the whole thing probably added anywhere from 40-50 horses, and i love it. and i also now have this high pitched winding noise now..it actually sounds like im driving a ford lightning. but i was wondering if anyone has done this before and has had any problems with the supercharger or drivetrain