My truck has been running code 44 for about a month now. At first, it was just the light. A couple days later, the idle became rough, and I replaced the O2 sensor. This fixed the issue for about 200 miles until the code and the rough idle returned. I replaced the O2 sensor again under warranty, and it worked fine for another week or so. During this time, I replaced the fuel pump when replacing the sending unit to upgrade to a 20 gallon tank, so I do not believe the fuel pump to be the issue. About a week after replacing the O2 under warranty, the code came back. It has been about 2 weeks since the code came back. It does not idle rough, but it does occasionally stumble at a specific RPM while accelerating. When the code came back, I replaced the O2 sensor with an AC Delco unit, thinking that the Bosch sensors were just hitting the fan. The AC Delco sensor made no difference. I replaced the fuel filter (about 30,000 miles on the old one) and ran some fuel injector cleaner through the tank, but those have made no difference. My book says to test the MAP sensor by unplugging the connector, and that the ECM will substitute default values for it. If the MAP sensor is bad, the lean condition should go away after unplugging the sensor. After unplugging my sensor, it ran worse, and stalled out when I tried to drive. At this point, I'm torn between replacing the exhaust manifold, or tearing the TBI apart and replacing the injector and pressure regulator.