sfk, I haven't replaced the IP diapgram in any of my cars so can't help there, but I have suggestion for the erratic idle (it is only revving when sitting at idle right?)
In my W123 (can't remember in my old W115) the idle will surge when I leave the 'idle-speed' switch on the dash in the far-right (starting-only) position. Try playing around with that first by backing off the starting position. When my car has run funny in past, I could always tweak the switch to lower/raise the idle to a point where it was smooth.
As for smoking at start up, it may be your diaphram in addition to the IP timing. I've replaced just about everything there is in the fuel delivery/filtering system in my W123 and it still smokes on cold start and even at idle after warming up. As I understand from several sources - the IP timing is the likely culprit - make sure and get the IP timing set properly after getting the new diaphram in. It could be one, or any combination of the above items.
'95 E420 - 'Shadowfax
'92 Volvo 740Turbo Bard
'74 240D - 'Ol' Green
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'77 300D - 'Red
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'75 240D - 'Bianca the Blue Bomber