Thanks Mike, but the problem was elsewhere. It is however solved! Here´s the story:
I went to my trusted indy to the regular maintenance. Mentioned the high idle and he shortly find that the hose clamp between mixture control and throttle assy was loosen and broken. So it would leak air after engine has warmed up and then raise idle. He told me that the one who replaced the throttle switch is responsible for the broken clamp. It was the dealer who did the replacement.
I went to the dealer and insisted that they would replace the clamp under warranty. They really resisted but eventually agreed. The new clamp did not cure the high idle. But the dealer found that the ignition timing was 13 degrees off the factory spec!!! The timing was adjusted to spec and the idle is now perfect!