So I attempted to remove the modulator to test it, and I promptly stripped one of the allen bolts that hold it in place.

So I followed Steve Brotherton's advice and adjusted the modulator for practice anyway.

Well, 3.5 turns ccw and the car shifts perfectly- hot or cold, at all speeds.

The previous modulator rubber cap was chewed up, which should have clued me into the idea that someone had been messing around with it. I think that they attempted to adjust the modulator to compesate for all the other vacuum leaks that they otherwise couldn't diagnose and repair.

So I believe that this is the end of the story on my hard slamming SDL transmission.

thanks everyone

__________________
84 300TD - 235k - Farbe "Surfblau" bought at 213k
87 300SDL - 131k - Farbe "PimpGold" bought at 115k
00 Klepper Faltboot Expedition Double