Hello I am new to the forum and buicks. I have just aquired a 1991 Buick Regal GrandSport with a 3.8l engine. The engine was running rough and stalling at idle when I got it as it was not run for 7 months. Service Engine Soon light was on and I ran codes and got code 34 MAP sensor and code 41 for cam positioning sensor. I do have factory gm service manual and followed all the testing trees in the manual. Replaced both sensors and found some wiring issues around the block for the the cam sensor. I pulled out entire harness from ignition module to the 8 way plug and repaired all of the wiring. Cleared the codes and restarted and only had code 34 map sensor low voltage. I checked the voltage from the ECM to the map sensor and recieved .49 volts. Checked other wires from the MAP plug for shorts to ground and to the other wires. I figured as the manual said the ECM was faulty as it was not putting out the 5volts reference needed for the sensors. I changed the ECM with a refurbished one from NAPA and now runs good with little to no stalling, maybe once in ten minutes, but the code 34 still exists and the voltage from the new ECM is still .47-.49 volts. I am getting frustratted as I am lost to what to chevk next. Am I missing something or some wire to check. All inputs to ecm that require 12volts are getting it and the grounds check out. Any thoughts from you experts?