Need Help Engine People

[CMYZGO]

So my car has a hanging high idle. When I start the car it idles at 1K. When I drive the car around it will act fine while its under power. As soon as I take it out of gear/push the clutch in, the idle will jump to 1800-2K RPMS. The RPM's will hang until I come to a complete stop, at which time they will fall back down to 1K.

Some more info.
The car only does this after its warmed up. So if I hop in the car drive a mile down the road and push the clutch in the RPM's will fall back down like they are suppose to. If I am cruising along at 1400 RPM's and push the clutch in the car will automatically climb back up to 1800-2K RPM's until the car comes to a complete stop.

Last fall I asked about this same thing and most people suggested that it was a vacuum leak. Well I started the car up earlier this spring and took propane all around the vacuum lines and intake and never got a response out of the car, so if it has a leak I can't find it. I also cleaned the MAF, while cleaning that I also took out the IAC and inspected it.

I took the car for a good ride this morning, to see if cleaning the MAF and checking the IAC did anything. Initially it was acting like it should, IE, I push the clutch in and the RPM's fall instead of climb. About 15 miles into my drive it started to hang again. I also noticed that the harder I get on the car the higher the RPM's climb once the clutch is pushed in. Enough that it sets off the SES light for "High Idle."

I'm fairly mechanically inclined with older engines and small engines so when it comes to all this computer controlled stuff I have no idea. I had my uncle ride along with me and he didn't think it seemed like a vacuum, but again he doesn't know newer engines.

The car has LT's, ORY, LS6 intake and a mail order "Tuned by Frost". I also noticed it has a catch can installed, but it was installed wrong. Its routed from the clean side, instead of the dirty side. I didn't do any of these mods to the car, the previous owner did.

So any help or other directions would be appreciated. If anyone in the area wanted to check it out I would greatly appreciate it. I live in Howell and work third shift in Jackson.

[meissen]

For ya - not familiar enough with the LS engines to be able to help.

[SS4Matt]

It's more than likely from that mail order tune. My car used to do that "sometimes" (but not even rev that high). I would get a hanging idle back when my car was just a head/cam car maybe 1200 at most, and settle back down to 8-900 rpm

[CMYZGO]

Now they are saying its not suppose to rain here today so I am going to take the car out and video it.

[sman]

Ive seen this on several cars. 2 out of the 3 that ive heard of were tune related, the third was a piece of junk Nikki Williams 90mm throttle body.

[SS4Matt]

Ive seen this on several cars. 2 out of the 3 that ive heard of were tune related, the third was a piece of junk Nikki Williams 90mm throttle body.

There are a lot of drivability issues that can't be done via mail order tune. That's why my car was drove all around and street tuned for that kind of stuff.

[sman]

Yup, I agree. A street car needs a street tune. No other way to get it dialed in correctly.