1994 high idle

My 1994 Bonneville, non supercharged, is idling at 2500-3000rpm. Have replaced idle air control valve. Had a friend hook it up to computer and nothing specific found reference the idle. EGR and MAF checked out ok. Throttle body seems ok, butterfly not sticking open. He said it appears a large amount of air is getting into the engine and the computer is adjusting for it by increasing the fuel flow. Can't find where the air is getting in though. Can't find any vacuum leaks, have already replaced some vacuum hoses. Anything else I should be looking for.

Check the TPS for proper voltage. Should get a 5v feed and have 0.30-0.70v with the key to run but not started.

Vacuum leaks are very common and sometimes very hard to find. Even tiny leaks can cause a big problem. Your friends scantool should work for general leak detection. Hook it up and look at the 02mv and fuel trims. If, at idle, the o2mv is very low (constantly below around 300) and the fuel trim #'s are high (above 128) it's usually an indication of a leak. Not to say that can only be caused by a leak though.

Aside from that it's always good practice to pull and clean your throttle body. Even a tiny amount of dirt can cause idle issues.

Good luck.