40+ horses is alot so I would look into either a supercharger, turbo kit, or nitrous. If you're goal is a little lower, say 20~30 hp, a cold air intake, headers, and free-flowing exhaust/cut outs could probably be enough.
the only other options between forced induction and the basics is engine work, which is alot more expensive. Also if you go forced induction, make sure you get it tuned at a performance shop. a proper tune is the most critical thing to do after adding a substantial amount of power over stock.
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