I haven't changed mine out yet, but in the manual it lists two different ones, a NGK and I cant remember the other one. I went to buy a few at the local NAPA, but they had to special order them. I've had the stock one in there since august 08.
2008 700xx; Power Bomb header with power core 4 exhaust, Power Programmer III, pro armor nerfs, prm products control front and rear bumpers and full skid, 10" ITP rears, ITP Baja's fronts, RZR 2's all the way around, Uni filter, 13t sprocket, CCP steering Damper, DS450 shock swap, Dual Gasser Throttle, bar risers and Moose barkBusters. 730XX kit plus other engine mods!