Ok I wasnt going to chime in here as I really had no answer to what your problem might be,but after a little thinking here is my In your first couple posts you indicated that the left bank wasnt working at all, you said that you put a plug in the wire and checked for spark and had it! So what makes you think that the whole drivers side isnt working? If the plugs are firing and correctly then the cylinders are working in that aspect. All the responses to the fact of a vaccum leak and bad carb are not going to be the answer as that would affect how the whole engine operates not just 1 bank. I had a 72 Firebird many years ago that I did a tune up on, the car fired right up but upon revving the motor it had a miss and ran rough,well guess what, I had left all the left side wires laying across the top of the motor. I was amazed it ran at all with only 4 cylinders firing. You said it ran fine at higher RPM's. I guess if the motor has sat for any amount of time then the springs that were compressed might not be closing those valves properly. Or another situation could be the use of unleaded gas has buried the exhaust valves into the seats causing a loss of compression??