A question on cold start idle speed...

[Dr.Outback]

I've done some extensive research on the SVX's idle system because of an apparent problem I'm having with the cold start idle. When I get in and start the car, the engine quickly starts and revs to about 1500rpm. That's normal. But the engines revs that high for about 3mins after driving down the street. Do any of your SVX's do this? I can't find anything in the service manual about normal cold start idling. I was thinking that maybe the Auxiliary Air control valve's bi-metal spring is no longer heating properly. What are your ideas? Thank's.