I've searched the topic and have found some useful information, but I'm still stuck.
History...
-Cleaned the throttle body last night the CRC cleaner. Removed the throttle body from the manifold.
-Thought I might remove the coolant lines from the ICV but realized that I'd have a mess if I did, some coolant squirted out.
-While I had the throttle body off I figured I'd do the "O" gasket mod. So I cut the "D" out and cleaned up the shavings.
-Put everything back together and checked all electrical and connections.
-Started the truck and revs pretty normal for a slightly warm engine.
Driving...
-While in gear with brake at a stop light the revs are smooth at around 1000rpm.
-Pop it in neutral and the revs jump to 1500 rpm again smooth. Same for park.
-During a cold start up its rough and I have to give it some gas, the revs will steady out at 1000 rpm then climb to 1500 rpm and remain steady. Obviously opposite what what's suppose to happen.
-No check engine light.
So what is it?
1.) ICV idle control valve
2.) TPS throttle position sensor
3.) Can't imagine it's the "O" gasket.

did you ever fixed the problem?

Sure did. Everything seemed to have corrected itself. If you're having the same problem just let the computer reset itself and everything should get back to normal, as that's all I did. If its not going away then its something mechanical.

I'm having the same issue, how long did it take for the computer to reset?

I first started the truck I thought the damn thing was trying to blow itself up, so I let it run for about a min, then shut it down. I pulled the EFI fuse under the hood and left it out for about 30 min. While I was waiting I worked the throttle cable about a dozen times or so just to get some play on the TB butterfly, thinking that I might need to really work in the cleanear and make sure it didn't sound like anything was sticking. After that I put the EFI fuse in started the truck back up and took it for a drive, this time when it idle'd down, it was right back to where it needed to be.

About two weeks ago I took the IAC valve out and cleaned it and it has since returned to normal, valve was pretty gunked up, probably from when I clean the throttle body! Just wanted to post this incase someone else was searching for a solution to this problem.

Thanks guys.

I was having high idle issues after cleaning my throttle body and after reading this I double checked everything and found a loose vacuum line. Fixed that and checked idle.

Back to normal!

Just in case others see this post mine was caused by a coolant temperature sensor.

While on the diagnostic computer it would read from -18 to 210 degrees. This would cause the exact symptoms others stated.

On mine I would see days of perfect operations and then fine in drive and 2000 rpm in neutral and park and a hard start when warm.

I tried cleaning MAF, Replacing MAF, Replacing TPS, Cleaning throttle body, checking vaccum lines, Cleaning IAC, replacing IAC. all to no effect.

Here is hoping that this Coolant sensor is the culprit for me.

Having same Hi-idle problem.Did cleaning the IAC solve ur Hi-idle problem?I've checked for vacuum hose leaks & removed/cleaned TB still getting 2000 rpm after 5 min.Hava 98 4runer ; 4 cyl.

Mine always idled around 1500 at cold starts then automatically goes down to 1000 later on. Seems normal. No?