I have a 305 tbi with about 110k miles on the motor. I gave it a tune up (plugs, plug wires, cap, and rotor) a couple months ago and it ran great. I do have a couple mods..headers, exhaust, open element, no smog pump, chip.

Here's the question... Sometimes it idles a little high when i stop for a few seconds (like at stoplights) it will eventually go back down to idle at about 600 rpm. It just takes about 20 seconds to get back down there. also it seem just a tad more sluggish than it did a while back. I didn't replace the O2 sensor when i did a tune up and i'm assuming it's probable the original from when my car was born. Could replacing that possibly help the old beast out??? (i know it won't HURT, but i was just wondering if it could possibly be the culprit for the slow move back to idle)

 

Check the IAC, it gets fouled with carbon and it can't control the idle properly.

 

how do i clean it if that's the case??

 

Pull it out and clean it with compressed air. I have heard that cleaning it with carb cleaner ruins it. There is a tech article on how to adjust it on this site.