You raise a very interesting possibility. I think the idea has some merit. I have had two 740s--the first one was an 89 745 GL, with M47. My current car is an 88 745 GLE (B230F, not 16V) that was originally an automatic. I have since converted it to an M46. The character of the two cars is surprisingly different, and agrees with your observation. The 89 loved to rev, and seem to thrive on being flogged, whereas the 88 is a torque monster by comparison. I continue to be amazed at its lugging ability, and rarely wind it over 3000 rpm. Of the two, the 88 gets noticeably better mileage---29-32 as opposed to 25-28.

Unfortunately I don't have a spare ECU from a manual transmission car I could swap in to test the hypothesis. I have one of the correct type, from an 86, but it had a ZF automatic, and two from 90s, both manual, one 16V, which are the late type for crank timed ignition. Maybe I'll try to pick one up the next time I'm at the junkyard.