A final update on this problem: the car continued to have low power, poor cold starts, random cut-outs when accelerating, and the A/C stopped working; I happened to to be using my multi-meter at the diag socket to remind myself of the polarity noticed that with the car idling, I was getting 18v! I replaced the voltage regulator on the alternator and everything is back to normal.

This is something I would have never suspected.

__________________
as ever
Paul

1989 560SL
1987 300SDL
1987 300TD
1983 BMW 633CSi
1972 280SE 4.5