Megasquirt ECU

IIRC, FM says a Link ECU can add 20 hp to an NA, if it's fine tuned on a dyno. I doubt the Megasquirt is much different, except for the much lower initial cost and the much steeper learning curve. Note that you lose emissions control, if that's a factor in your location. I don't know how OBD-II is affected, but at a guess it will be disabled.

These replacement computers are intended for cars with more than 6 psi of boost, for which the inflexible OEM ECU cannot provide proper fuel and timing control. 20 hp is barely enough to feel a difference; a low-end supercharger should add over twice as much power, and be considerably easier to install.

It would be an interesting project for someone who's more concerned with gaining an education than ultimate results.