Check the big vacuum connection on the back of the upper intake, the one the brake booster hose connects to. I had a leak there and couldn't figure it out. Pulled the connector out of the UIM and ran some RTV around it and stuck it back in and let it cure. Next day fired it up and all was well.
Other than that it still sounds like a vac leak somewhere to me. Try spraying carb cleaner while the engine is running around where the UIM meets the LIM, throttle body, injectors, any vac lines, etc. and see if you get the idle to change. If you find a spot that makes the motor idle change then that is a vac leak and needs to be fixed.
