i had a 75 shot on my h23 also. i upgraded the fuel pump and used the zex spark plugs. it ran great. make sure the nitrous nozzle is at least 12" from the thrrotle body, i had mine as far as i could put it for better distribution of nitrous before it reachs the engine. make sure timing is 0 for 55shot, -2 for 65shot and -4 for 75shot