I'm sure Benzmac would concur that the most common reason for 606 engine surging is caused by sticking resonance flaps. I an unsure what or even if codes are set by the flaps sticking. There are 2 of them, one in the middle of the air tube on top of the engine, the other is under the intake manifold near where the air tube attaches. I did fix one 210 chassis Diesel recently, very high miler, which was fixed by adjusting the pump timing.
Gilly