A buddy of mine has a 400Z and just this weekend we put a pair of hot cams, K&N air filter, and TRIED to put the dyno jet kit in it. We cant figure out what size jet to get it perfectly right. I think we have a 155 or maybe even a 160 in it now and he says it still dont feel right. If anyone could give us any help, we would be much ablidged

 

did you check the plug? Does he have an aftermarket exhaust? I had to put a 165 main in mine for a slip on exhaust, plus turn out the air screw about a quarter turn.