Unfortunately the airflow potentiometer is only available preset on the airflow meter. It isn't as expensive as that would seem but the labor to replace it is also a bit as the whole thing is replaced which requires all the adjustments to the fuel distributor. Its a bunch cheaper than the fuel distributor.

As to temperature. I imagine it has to do with the amount of airflow at idle. Once warm the amount of airflow at idle is lowest and also the largest portion of total one spot movement. This is the place that wears out first and is also the time when the idle is lowest. Because of this I would highly recommend the simple rpm fix. Not only will it give you more idle to oppose the problem but it will also add more air so the airflow meter will be it the position that seems to work better.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician