Higher than normal Idle, and occasional stumble

[Billy Mild]

I have been struggling with a higher than normal idle since I pulled the plenum a few months ago. When I pulled the plenum the following things were replaced: Plugs, Wires, Fuel Inejctors, and fixed any remaining vacuum leaks.

Sometimes my idle will hang around 1500-1700 RPM. If I stab the throttle really fast it will go back down to 900 RPM. I have noticed that when the engine is still cold, not fully warmed up, the car will sometimes stumble around the 2500 RPM when I go more than 50% throttle. If I go WOT it pulls through it without issue. There seems to be a sticking point around 50% throttle. Once the car comes up to full temp this issue becomes less noticeable. I haven't tried to spray the throttle blades with lithium grease or anything.

I have read a few old threads concerning the idle issues. It seems that may be related to my Throttle Body needing a service, or there could be a vacuum leak somewhere. I don't think there is a vacuum leak since my secondary vacuum pump will run for a few seconds with the key on, and shuts off for a long time. I tried to do the IAC reset procedure. I drove just a little bit after that and the idle did seem better, but still not perfect.

Any ideas?