I got done installing a new K&N FIPK complete intake replacement late last night. Been out this morning running errands. Definitely a felt performance increase Throttle response is improved over the full RPM range, but you really feel the difference as you hit about 3000 RPM. And hear it as well. Sounds sweet.
I had a cutout factory airbox with a factory filter. Big difference over that. In the box, K&N included a graphed printout of "typical power gained" from 3000 to 5000 RPM compared to factory 4.3L S-10. This is what they say you gain: 4.2 hp @ 3000, 5.6 hp @ 3500, 7.7 hp @ 4000, 9.1 hp @ 4500, and 9.2 hp at 5000. Who knows if their numbers are right, but it is noticable.
Well, that's more air in. I have a Gibson 2.5" cat-back exhaust coming this week to get more air out.
Throttle response is improved over the full RPM range, but you really feel the difference as you hit about 3000 RPM. And hear it as well. Sounds sweet.