Harumph. Checked the links. I don't see almost any changes so far, to what I have from years ago in my original old copy of the chart. I've added a bunch of comments on EGR in my updated copy, since I have to deal with that regularly.

The LH2.0/2.1 thing continues to be a curiosity. Before I changed my 83 coupe to 2.2 we did some playing around. I plugged in both the 503 and 510 ECUs and checked the exhaust temp. At idle for 30 minutes the 510 ECU ran the cat between 15 and 20 degrees hotter. Howzat? The 510 ECU affected nothing else, but over the course of two tanks of gas my combined mileage went up just under 1 mpg. Granted, two tanks might not have been enough of a sample, but the exhaust temp and this may be related. The car has a B cam and a full, 2.5" exhaust. I didn't notice any difference in feel with either ECU as far as performance. Seat of the pants though. I'm getting to the point that LH2.x won't be much of an issue. When that happens, it would be neat to open both ECUs and first see what the physical differences are. More to the point, I'd love to have someone read the maps and see what changes--if anything. If indeed there is something significant, I'd be willing at that point to say the 510 ECU is "2.1". As for the turbos being 2.1, I just pulled the ECU out of a dead 4/84 production date 740 turbo at the yard--a rare bird. Surprise, it was a 503! Not to say it was not changed at some point, but generally I've not found either to be problematic, so I expect it was original. So much for turbos being 2.1.

On the turbo/non turbo issue, there was a post someplace about the ECTs varying, and this being the issue, but that's not so. For example, the 2.2 ECT is the same for 7 series turbo and non. No reason that would change. What seems silly is to assume that the fuel mapping would not be different for the turbos. When one takes into account lag, boost--just to mention basics, it would make no sense that the ECUs would be the same. My problem is in the misuse of the words "compatibility" and "interchange". Interchange implies that functionality will be identical. Compatibility means you may slide by. I can't imagine an NA map would provide for all the needs of a turbo, but I'll bet differences would be all but invisible in very basic, light load driving.

The 933/951 post you mentioned is one of the primary things I'd like to debunk. 933 for 91-92 EGR cars makes perfect sense because they are CSV cars also. What I don't understand is the 935 for 92-94, which crosses the CSV equator. Again, compatible, but putting it in a 92 is probably fine, the CSV just won't work, but if it has CSV capability and the 94 has no valve the car probably won't start in MN in January--(a long way from the equator in distance and warmth).