Dave, I'm worried that the new pot is apparently different from the old. The difference in total resistance is significant, as is the need to find a different setting for idle. The behavior you note could well be due to the differences.

It is reasonable that your idle is steadier - after all the instability is caused because the old pot had an erratic output - the new one is steady. To restore proper operation, though, you will likely have to get the correct pot. Look at it this way - if nothing else, you have diagnosed the idle problem to the airflow meter. If you have to shell out for the MB part and calibrate it, it should solve your problem. Perhaps someone on the board with an 8V or M103/4 will buy your new pot.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7