I just put in K&N FIPK air induction system in my 1994 4runner & it is great! I can certainly feel a difference in throttle response (although have not measured). It also sounds great, especially when you really punch it.

I also replaced my stock muffler with an original Flowmaster 40 dual chamber which I am pleased with the sound - nice deep throaty sound but not as loud as the V8 (unfortunately). I also recently installed the Downey 1.5" HD springs which make it sit much better.

The air induction will be a definite on any car that I have - it's amazing how air restricted they run from the factory.