83 Pontiac 6000 2.8 Z Carb With Drivability Problems

I have a 83 STE with an 2.8 Z E2SE carb with drivability problems - hesistation, surging and rough idle. The problems looks to be from a lean condition caused by the carb, because when I disconnect the mixture control
solenoid (max rich) the drivability improves. This includes both open loop and closed loop modes. I've checked most of the obvious stuff- vacuum leaks, plugs, wires, ing timing, fuel filter, O2 sensor, Mix control solenoid, and no ECM codes. So the lean condition seems to be from a problem in the carb. Anyone know if there are any typical failures in the carbs that would cause this?
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Aside from carb problems, the egr was famous for getting carboned on the pintle and seat causing these exact symptoms, check this out before the carb work

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Try disconnecting the EGR (engine not running) and drive it around the block. If the symptoms clear up, you've found your problem. DO NOT drive the car any distance with the EGR valve disconnected/
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