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1990 Chevy G20 code 44

I have a 1990 G20 Chevy Explorer Conversion Van showing a code 44, lean exhast. I have had the van for about a year. It has a new 350 CID engine with about 6000 miles. Recently the engine started surging and stalling. The fuel pressure was low, 5PSI, and a new pump was installed, but the problem remained. I soaked the injectors in mystery oil and carb cleaner and found a considerable amount of water was in them. I reinstalled the injectors, replaced the gas and the problem remained. I found the plug for the MAP sensor was damaged and replaced the pins. Same problem. I have not found a vacuum leak, however I notice the IAC valve buzzes and vibrates when in the code reading mode. When I check the pins in the IAC Valve connector with a test light the A and B high circuits light but the A and B low circuits do not. When I check with a volt meter the A and B high have about 11 volts and the A and B low have about .5 volts. The MAP and TSP sensors appear to be fine. The oxygen sensor is new.

My questions are, were the injectors damaged by the water, should hould the IAC valve buzz in the code read mode, what is the voltage on the IAC high and low circuits and would it be high enough to light a 6 to 12 volt test light on all circuits. What is the most common cause of a code 44 for this year and model van with a 350 and 4 speed automatic.

Thanks,

Rick