1999 Ford Explorer Engine jumps and loses power

My 1999 explorer has a problem. I live in las Vegas and the problem only happens with is get hot (usually in the summer when temps are over 100) or if I drive it for longer than an hour in colder temps. About 30 minutes into driving almost on the clock when it is over 100 degrees, my engine will start jumping and hesitating. From a stop as I push in the gas, it will jump a lot, and or will not go over 1500 RPMs for a second or two then jump up with alot of power, then drop again. The harder I press the gas the more it hesitates and jumps. I have to drive in lower gears at lower RPMs to "mask" the jumping. It does not turn off or die. And if I park it for 10 minutes it will stop for a few minutes then start back up once driving. If it cools down completely it will take about 30 minutes again. If I push in the clutch, my engine will rev up in RPMs no problem however, trying to move the truck the problem occurs. My check engine light is off, I had the O2 sensors replaced, because the mechanic I took it to said that would fix it. And I replaced the MAF sensor about 30,000 miles ago and it was happening before then. As long as the problem is not happening, I do not smell gas. But if the problem is, then I smell gas.

Also as the engine warms up, there is a lot wining or humming sound come from the engine during idle. Even if the problem is not happening.

If I could stop the sound coming from my engine and the jumping/hesitation problem that would be excellent.