[LX5liter]

The easiest way to get a good seat of the pants increase is to add a supercharger. Keep the boost fairly low (5-6#) on the stock engine. As you add better parts (bigger MAF, throttlebody, injectors, etc...), you can up the boost a bit, but don't go much past 9-10#s of boost on the stock bottom end.
You can also go the nitrous route, its cheaper on the original cash outlay, but you have to re-fill the bottle(s) once in a while.
Then there are turbos. They work great, but take up alot of room. I think next time I build another car it will be a turbo.
Whatever you decide, get a kit designed for your car, it will make installation alot easier.