OK, here is one for you. I have an occasional running problem on my 02 5.3 Yukon 85k miles. The problem only occurs about half the time and I can't figure out what it is. Here is the best way I can explain it. Most of the time ( a little over half) the Yukon runs great. smooth idle, responsive throttle, and great power. The other part of the time, idle is a little off, power not all there and throttle response not great either. I have tried to place it to the weather or gas. An example was Thursday, I drove to work and the truck was running bad. All the bad symptoms were present. I get in on Friday, and it is running like brand new! The temperature was the same on both days and I am on the same tank of gas. I have done sea foam, throttle cleaning and it didn't make much of a difference. Has anyone else experienced this problem??