Keep in mind a proper nitrous kit will run at least $1300 new. You can buy kits for alot less than that brand new (bare kits) but you will want to add things like a RPM window switch, electronic TPS, bottle heater, fuel psi safety switch, purge kit, some form of air fuel monitor, and so on.. I had your mindset a few months back and ended up piecing together a kit. Got the bare kit used for $400, and spent double that making the kit as "safe" as a nitrous kit can be. Never used it though, ended up selling it a month ago to buy a bike :P. And ditto on "NOS".. Its nitrous, not NOS. Dern TFATF..

Most 4cyls are good to 75hp on stock internals. You have to check your plugs regularly to make sure you arent leaning out a cylinder, if so youll probobly want to upgrade your fuel rail and pump. I wouldnt go over 100..