This makes me thinking about that fault

" also tried pulling the stomp codes from the car but it doesn't seem to respond. It's unclear to me if the 88s have this ability (Bently says yes, other places say no).

I took the car to the best ZF shop in the Bay Area (Peter Schmidt) and had them take a quick look at it. The first thing we did was hook it up to the computer (I can't remember which one). Just about every fault code popped up which we agreed didn't make much sense. They cleared the fault codes and the car shuttered a bit (strange...). After this we went for a test drive and the behavior was even more erratic. The car would go to 4000+rpm in 1st and then shift to 2nd."

As for stomp test: there can be 2 reasons:
old models sometimes had problems like PatrickC750 also with his 1988 car.
What is the actual production month? On my website below there is a VIN decoder, check that out and add those data as you signature, see on top under my account where you can add that.

The second possibility is that a engine cable is broken and therefore the lines to get a Peake signal are interrupted, also this funny test results from Petr Schmid. I had this once about 2 years ago. Limpmode, cracy things going on like the aircon suddenly started or switched off etc.
We changed almost all modules, the cluster, both MOTRONIC, EML, GM etc., nothing helped. Finally we measured all wires in engine room and we found out that 2 cables were lose / slipped out and had lose contact, that was the main conenction in the engine room. In my car I have 2, X20, X21.
Your car has one, which is thr round shapped connector besides the diagnosis connector in the engine bay on the right hand side.
Best is you measure the engine wires. I am not sure of course, but maybe that is a possibility.
Wiring diagrams are her
http://shark.armchair.mb.ca/~dave/BMW/e32/

E32 750iL 11/88, E32 750iL Highline 03/90
7 series Tech tips URL:http://tinyurl.com/3486c

• 88 735i Transmission problem (won't shift out of 1st) - abyss 2008-08-17 22:18:56 (139 views)
  • FIXED! - abyss 2008-08-31 15:04:25 (100 views)
  • Check all the wires. The S/E/M tarnny switch swap it - alv12 2008-08-18 00:07:54 (69 views)
  • Re: 88 735i Transmission problem (won't shift out of 1st) - az735i 2008-08-17 22:39:28 (65 views)
    • it could a broken wire - shogun 2008-08-17 23:18:22 (71 views)
      • Re: it could a broken wire - abyss 2008-08-18 01:45:20 (62 views)
        • the blower fan problem might be a bad sword (url) - shogun 2008-08-18 03:06:15 (93 views)
          • How to check engine electrics - abyss 2008-08-18 13:28:12 (55 views)
            • that is a good basis for checking - shogun 2008-08-19 01:23:48 (55 views)