Sounds like the air valve is broken..............
(under the throttle valve; 2 air hoses and 2 coolant hoses attached to it, and a 2 wire electrical connector)
Has an internal air valve controlled by an bimetallic strip; As the engine warms up, it closes the valve. If the electrical connection goes bad (can be internal or external) it pretty much quits working.
It's very pricey. You can tweak it close, or plug up the hoses, but you need to raise your warm rpm (about 1000) so that engine will still run when cold..........
