Rough Idle

[Elwood]

Just got a tune up in Bakersfield, Ca. from Chuck. Trailered my Porsche to Prescott AZ. The altitude is a big differents. The car is old, stuff goes bad. I had to adjust the idle. At 1200 cold seems a little high but after 30 min. the idle goes to 950 to 1100 RPM. If lower than 1200 at start after 30 min. idle goes 650 to 1000 or dies. The motor is a 3.0 F/I. I think I know whats bad but I don't want to fix something else that's not bad and not fix the problem. Has anyone had this problem?