I'd take another look at what RT1 had to say. Sounds like the Air Regulator Valve may be stuck open:

Quote
The big tube one off the throttle body (throttle air control valve?) should close (like a choke) in a few minutes when the engine heats up to block excess air. It's electric (heating element) so if the wire or element is bad it'll stay open


I've been having the opposite problem - rough cold start & idle, everything normal at regular temp. I think the air reg valve is stuck shut. PITA to get to, totally buried under the intake manifold...

2.6 Trooper
2.0 Impulse Turbo