The ultimate bang-for-your-buck upgrade will be a 55-shot Zex dry nitrous system.
Assuming your motor is in good condition, that's my recommendation.

You will need to upgrade your clutch and swap in colder spark plugs. A short-ram intake, exhaust header and cat-back exhaust will complement the nitrous oxide system nicely.

For about $1100 in parts, you'll make roughly 150 hp at the crank with the nitrous off, and about 200 to 205 at the crank with the nitrous system activated.

Brett aka Master Yodub, is one of our resident authorites on nitrous oxide systems.

Run a few searches with the keywords: ZEX, Nitrous, B18A, Bolt Ons. The search results will give you insight into what gains you can expect from various mods.

And before anyone brings up the Tornado or SpiralMax...stop. :a:
They are pieces of shit that do nothing to increase power.

And as a rule, if you're making more power, you're obviously burning more gas. So don't expect to get 35mpg if you're constantly using the nitrous oxide.

Lastly, welcome to HAN. :cheers: