There are a bunch of different ways you could introduce nitrous into an engine.. yes, there are systems on the market that have progressive controllers that are adjustable from mild to WILD, 2 Stage systems, like you mentioned, are STILL IN USE today (two systems) BUT,,, there is a WORLD of advancements that make a 2 stage system basically OBSOLETE!!!! I've NEVER ran a nitrous kit on my racecar (YET!!!) I am right at SUPERPRO (it runs LOW TENS) and I want to keep running PRO for a few more years before i run with the BIGBOYS!!!! A 1000HP stroker motor on the bottle would put the challenger in the LOW EIGHTS and the chassis is only certified for 8.50,,, So,,you see,,, ANOTHER CAR is in the future!!! I saw a JET CAR on EBAY and I'm watching it (twin jets).. I'm NOT READY to buy someone elses headaches and I'd rather build my own!!! I'm pretty good with the GTAW (tig) and I know enough ( I HOPE) to put together a JET DRAGSTER!!! I have a friend who has TWO and he JUST retired from XEROX and MAYBE I could talk him into spending some time with me this summer... he wants to do the circuit this summer, so lets see what happens!!! As far as using AFTERMARKET pistons,,, YAMAHA pistons are SINTERED aluminum and sintered aluminum pistons are WAY BETTER than ANY aftermarket pistons out there ON THE MARKET!!!!! I'm SURE you could talk CP or DIAMOND into MAKING YOU SOME ABSOLUTELY WILD PISTONS,,, BUT,,, STOCK YAMAHA PISTONS are ABSOLUTELY THE WAY TO GO!!!! Depending on HOW WILD you want to go with a nitrous kit, you need to CERAMIC coat EVERYTHING inside your combustion chamber.. I had TEFLON coated skirts and ceramic coated domes,chambers and exhaust ports. I SPRAYED almost 100hp into that SRX!!! You MUST weld the crank,Different heads, different rods (homemade) different carbs, different exhaust, different primary and secondary,different belt, and homemade pipes... DEPENDING on HOW NUTS you want to go.. You could even go the NITROMETHANE route!!! IT WILL NOT START in the wintertime (although theres a guy out there that has one and it starts in the wintertime),,, but,,, MOTORS like that DO NOT LAST TOO LONG (about 10 seconds) and the cost is ASTRONOMICAL!!!! I'm STILL TRYING to figure out WHERE THEY GET THE AIR from for that TWIN JET car on EBAY??????????