a big think that I have heard of/felt is to get rid of as much mass as possible. its amazing how much 100 lbs can do to performance. i have also thought of a supercharger, and I asked a shop around here that i happened to drive by, and they said they could do a supercharger, with a custom dyno tune, for around $6000. If i had that kind of money lying around I might think about it
, but other than a supercharger, all i could really think of is to change the cam shafts, use different intake and exhaust parts, or get a turbo...
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, im sure others have better advise, but that is what I think.