anything close to s 40 shot and valve springs are a big issue. done 3 nitrous stk motor setups this spring. done right requires valve springs, inj's cleaned/flowed, high flow fuel pump, good fuel, allows afr to be safely tuned to 13/1 for max power/torque. as mentioned spraying nitrous with ignition kill will cause sonic boom/pop that can spit shims or valve retainer keepers, fuel kill completley eliminates this problem. makes nitrous undetectable during shifts.i only install nitrous with a controller. nos mini is great simple unit with all the safeguards including programmable beginning/ending rpm and nitrous can be ramped in as needed. no need to turn nitrous motor where ur rev limit set. just got stk 06 gsxr 1000 tuned fri with above mods, small dyno verified 32 shot made over 100 ft lbs torque at 8300, shutting off at 12500 with over 200 on tap. u need to gear for the torque, not rpm. the torque nitrous produces makes for incredible accleration.