If everything is quality and the pistons are aftermarket...you could get away with a 125 shot wet direct port all day. I ran approx 80 shot wet on a factory b18a1 with 80k miles and after 2 bottles it still came back with stock compression across the board. Its all in how you hook up the nitrous and you will deff want a wet shot and direct port is the best of all the nitrous setups.