A different idle problem?
 

I've searched the forum and found lots of people with fluctuating idles or cars that can't idle. My idle is steady, but high.

When I start it up, it goes right to 3000 like its supposed to, then drops to 1500 like its supposed to, but then goes to 2000-2500 and will happily idle there much to my chagrin.

From what I've read, its probably a vacuum leak. I don't know the first thing about the vacuum system. I've got a Haynes guide, and I see the diagram but its tough for me to decipher. I'm still pretty new.

How can I find a vacuum leak? I tried listening for the hiss of leaking air, but its loud under the hood at those revs. It looks like hoses go all over the place, and are mostly out of sight.

Or am I way off base? I can't get the intake duct off to check the things on the back of the intake manifold cause my friend has my socket set.

Advice?

'88 GXL, K&N filter. The rest, stock.

First, get a copy of the factory service manual (free) from one of the links in the 2nd gen FAQ and try setting the idle according to the instructions for your particular model (i.e., Turbo or NA).

Probably a mis-adjusted TPS or idle mixture

Are those things that could have gone wrong overnight? Because I've had the car for over a year and it just started doing this in December.

TPS can, but idle mixture is something you would have to mess with yourself with a screw driver