Have you checked all of your vacuum hoses and intake bellows for leaks/cracks? If you have air ingress anywhere past the MAF these engines can display weird symptoms and get a little squirrelly to diagnose. I went through all this with my 744, found a split in the intake bellows which solved the majority of the idle issues I had. The throttle had been poorly set up by someone prior to my ownership too, so the TPS never engaged/disengaged...adjusting that up correctly remedied the rest of the issues.
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Barges of Distinction:
'96 945 SE LPT M90
'95 945 GLE D24TIC M90
‘88 745 GL B200E M47
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