some ppl have said to up the timing to 14 but i have gotten best result (track times) with it at 10. so playing around with the timing and the fuel pressure to get the best results
but to the original question, if yo wanna feel safe when using nos, 100 hp shot would be the most, without upgrading anything eventhough highly recommended to upgrade the fuel system and air delivery a bit. but anything higher than 100 shot and i would recommend upgrading fuel pump, injectors, etc...
boy it had been a while since i posted, that felt good, just been browsing latly