Idle Speed - Uneven and way to high

[Mike911SC]

I seem to have the reverse problem of what many have posted relative to idle speed issues.

My 1982 Targa 3.0 starts up at the flick of the key but then idles over 2k for about 3-5 minutes. It then slows down to aroun 1100 but then floats about 50rpm either side of that regardless of how long I drive the car.

The car runs like a champ but fuel consumption seems way to high which leads me to suspect a fuel mixture problem as one suspect. The exhaust also has a heavy unburnt fuel spell.

This may be a simple fix with the right gauges to set the mixture but my bigger worry is why is the initial idle so high (over 1k beyond the warm idle speed) and why is it floating once warmed up?

Any thoughts or suggestions?