Hey folks, wondering if some of the seasoned pros could help out with a super weird issue I am having.

So its regarding my 90 420sel.
A month ago I finally finished up the last stage in my a/c rebuild on the car by putting in a new condenser. And I filled up the system with 134a.. yea I know.. .. its all I had on hand to fill the system.

So far the system is holding a charge, and the cooling performance is as I expected with 134a.. semi ok.. I have r12 on the way. All my other vehicles use 134a so I have a few 20lb tanks of it.

My problem is definitely one of the weird ones I've seen. So I finally got around to trying the a/c and do some test drives around town, and im encountering a odd behavior. Ill kick in the ac, and the eco gauge will nearly peg to the right, and I literally cant get the car to accelerate above 60-70km/h.. It just wont go!!. Weirdest thing ive seen. Normally one would think the ac pressure is going way too high, but that's not the case. Ive tested the high pressure cutoff and its working as normal, and at idle, pressures stay within reasonable limits. Heres the kicker, I turn off the ac, and it takes about 15 seconds for the car to regain power, even though the compressor kicks off right away. So instantly im thinking its a fueling issue. But no where I can see if the CIS gets any type of signal from the hvac controller to tell it that the ac is enabled. I would think it would, to give the car a slightly higher idle when the ac is enabled. but cant seem to find any type of reference in the diagrams.

So heres part 1.5.. last weeked I decided it was time to do some R&R on the CIS sensors. I decided it was time to check the k-jet flow plate sensor readings as well as make sure I was getting a full throttle signal to ensure I was getting full throttle enrichment. Ive seem to be having odd performance issues with this car, even though the fuel system is in decent shape, and ive done a fair bit of work on it. So long story short, slightly adjusted throttle linkages to ensure full throttle, and installed a new plate sensor & calibrated. Overall car seems to run a bit better without the ac on.

Ok part 2 now..
Today I went to make sure my aux fans were working as expected, agian.. Just to rule that out.. And they were. But as I had the car idling in the driveway with the ac on. I would get random burst of rpm, and it would then settle down. I looked at the eco gauge, and over a 15-20sec period, the gauge would slowly move from the left to the center, then the engine would quickly rev up, settle down, and the needle would be pegged back where it belongs at the left.. then after a few sec, start to move to the center again (during this whole time the ac compressor continued to run! it did not shut off). Instantly I thought I should check the duty cycle. I pull out my multimeter. and sure enough.. it would start off at around 50%, where Ive had it set at all this time, then slowly creep down to 0%, then kickup, rev and go back to 50%.. Ah ha!! something is up here.
I turn off the AC, 15seconds later everything stabilizes, and the duty stays where it usually is around 52-47%

Only thing I could think of causing this... would possibly be the wires going to the EHA being backwards?? Or the CIS controller is on its last leg. Its like its trying to adjust the mixture, but in the end its doing the opposite of what it wants to do.
Is the EHA polarity sensitive? this car never really had the performance I would expect, my 560 would smoke the 420 on the street. I know its more powerful, but the difference is noticeable. Don't get me wrong the car doesn't run bad at all. It drives and idles pretty normal. But something has always been up in the fueling department.. like that last 15% is missing.

This one has me stumped

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Just my MB's:
1990 420sel - Winter DD - 410,000km
1990 560sel - absolutely showroom mint - 360,000km!