A cheaper way of seeing big power gains would be nitrous oxide. Really turbo is the only way to go if you wanna see big numbers. Start off by getting some aggressive cams, simple port and polish(not nessasary but a good thing to do), low comp pistons, and a decent exhaust with a t3/04 turbo kit(custom is way cheaper than a already put together kit). If you wanna get an already put together kit then I would go with a full-race kit. If you wanna see decent numbers with na i hope you got deep pockets or else it will never happen.