Been fighting a high idle issue in the 03 VGT after warmed up. It will rev as high as 3K and if I tap the pedal it will back down to 1.2k-1K. Here's what I've done.
Cleaned the IACV, and TB. Didn't help
Replaced the IACV with one from MWR. Didn't help, Also popped P0505 code occasionally.
Replaced the IACV , under warranty, had MWR rebuild a TB. Didn't Help and still will get a P0505 pending occasionally.
Cleaned the MAF and AIT. Didn't help (don't beat me dnm).
Replaced 90% of the Vac lines and tested every intake and Vac connection for leaks and found none.
Backed the TB stop set screw out as much as possible and adjusted the Throttle cable to be slack. Unfortunately the TB feels like it's stuck when first pressing the gas pedal.
3 weeks ago while on a 200 mile trip the car popped p0505, p0420. I reset both codes and had bounced it off the rev limiter about 2 times while passing in 3rd gear. On the return 200 mile trip it popped a p0446 and p0420 and again I had bounced it off the rev limiter 2 times. Reset them also.
This pass weekend on the same trip no codes not even pending. I bounced the rev limiter once.
Also once in awhile it will do the bouncing between 1K and 2K rpms.
Looking at real time data all the temps, pressures and etc look normal.