The OP's car is the same as mine.

M102.910 with the last series KE CIS transistorized ignition

As the head gasket has been off and "other gaskets" have been replaced I'd start by checking for vacuum leaks. Spray something like WD40 over the joints and see if that changes the idle at any place.

You should also check to make sure that all of the vacuum pipes are connected correctly.

__________________
1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!