Buy a decent cold air intake and header. Advance the timing 5 degrees and run better gas. Nothing you would feel in the seat of your pants but you would squeeze a couple more ponies out of it on the cheap. The only "real" power adders would be cam/s, heads, header and exhaust, injectors, ecu programming and a turbo with intercooler all done together. Ideally you would run a better quality oversize piston as well. So rather than blow 3 to 5 times what you paid for it...weeze a little juice with a few bolt ons and manually advancing your timing.