I'd set the timing to factory spec -- 4 degrees after TDC with vacuum applied for the 73 model according to the Chiltons manual. This will at least allow somewhat normal operation. I suspect you are setting the timing too fast -- never ever set it "by eye" or "by ear" -- no way that is accruate enough.

Verify that the advance is working correctly -- you may have a vacuum retard/vacuum advance set up, and if the hoses are backwards, all sorts of strange things happen. Been there done that, on the '68 Ford wagon!

As for setting mixture -- the Quadrajet instructions won't be all that helpful, as every carb has a different "basic setting" (ie number of turns from full closed to operation position on the idle jets).

The best system for setting idle mixture without a CO meter I've found is the Ford (Holley) procedure: Get engine running, then open idle jet until no more speed increase is obtained (rich) -- slowly close jet (going lean) until a 50 rpm drop, then turn 1/8 turn rich. Repeat for other side, the fine-tune both again.

If the limiter caps are still in place, this will be much easier.

One other thought about loosing power at 2000 rpm -- is you main jet system working at all? Sounds as if as soon as you get off the idle circuit you are starving for fuel. Check the instructions and make sure you didn't leave a gasket out of the emulsion tubes or something similar, or set the float way too low.

Can't be too specific, as I have always managed to avoid this particular set up (the one 280C I looked at was too rusty!).

I've gotten the perception that these carbs are kinda cranky, but if you persevere, you will at least get a drivable car, I'm sure.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!