Hello! this is my first post. I have been having an issue for a while. Its in regards to my poor truck stumbling when its up to temp. I wonder if what is actually happening is back firing into the intake.

Low down: When I first start the truck it fires right up and runs like a champ. If i keep driving it wont do anything for a long time. After about an hour straight, then itll start doing the stumble. But, I rarely drive that long in one given trip. If I stop somewhere and turn the truck off such as a store, when I start driving again, itll start stumbling when I get to about 35MPH and giving it throttle. It also is almost guaranteed to do it on inclines. The RPM will drop about 500RPMs. If I dont give it a lot of throttle, itll sometimes do it, but not as often. The other thing I notice is that when its cold/rainy i can do a round trip without it doing it unless I drove a LOT more than normal. But on hot days, it most certainly will do it.

Its only stalled once. But started right back up again.

I've replaced the dist cap, plugs, plug wires, EGR, IAC, coolant temp sensor, and a couple other little things. But it still persist. Im at my wits end and getting frustrated. Any thoughts or ideas would be great.