Had a problem this week I'm still trying to solve. Started losing power while pulling my boat to a local reservoir (97 Suburban 5.7 liter). Got past a grade I was pulling and it seemed to be fine. On the way home, had to pull another grade, problem returned but much worse. Had to stop the rig. Disconnected the boat to see if the Suburban could get me home without it. Heard some noise in the general area of the gas tank, hard to describe but not the fuel pump whine I heard in the past. On a whim, removed the gas cap (I had actually heard the gas tank making a 'thunk' sound while having the problems, and it relieved a bunch of pressure. Low and behold, it ran great with the cap off. Hooked back up to the boat and made it all the way home with no problems. Went to buy a new gas cap today, put it on, started having the same problem fairly quickly. Removed the cap, it went away. I checked the last few inches of the vent tube (from the filler neck to the rubber hose coming from the tank), no obstruction. For now, I am just leaving the cap just barely turned in, but I know this is not a good long-term solution. Any ideas? Anyone else have this problem? I really don't want to drop the tank ... I have had to do it twice before to change fuel pumps on this rig.