Have 2008 Avalanche with a 5.3. back in the early spring it developed a low power problem. Took it to a local shop and had them replace the valve covers and plugs. We had had another truck with a 5.3 where there was an issue loss of power smoking and that was the fix for it. While that did probably help some and overall running rough was not fixed. It was determined that we had a bad fuel pump. According to the person working on the truck it had 90psi key on engine off. We replaced the fuel pump, and it probably ran as good as it ever had until the oil pressure sensor went out the next day. Towed it back to them replaced the oil pressure sensor and I was back up and going. This is not my primary driver so it may sit for a bit until I drive again. Next drove maybe month later and did notice a skip especially at lower speeds but got me to and from my destination. Jumped in it late last week to take a part to someone. It fired right off ran for about 30 seconds and died. Tried again same result. It will always fire right back up after stalling. I check the codes only a P0449 is listed. Fuel pressure is at 40psi key on engine off. Will rise to 70psi key on engine on. Tried unplugging the MAF and oil pressure sensor to see if that is the problem but to no avail. The truck will always start on the on what to me sounds like the 3rd revolution of the starter and stall after 30 seconds. Any help would be greatly appreciated.