Question: On my Chevy truck, Hold the gas after a few minutes of running & the gas peddle sounds like it revs up & down by itself. See my video below.
Answer: By watching and listening to your video, it looks and sounds like that when you hit the throttle, it bogs down real bad, then when you let off it a little, it revs up. You said something about smoke coming out on the passenger side, but could not see it in the video.
It seems seems like you have a low fuel pressure problem or a plugged catalytic converter.
Low fuel pressure will not allow the engine to rev up because there is not enough fuel volume to get the RPM's up. Then when you let off the gas, there is enough volume to let it rev and then come down. An engine needs much more fuel under load, like in a full acceleration.
A plugged catalytic converter does not allow the engine to breathe, so the engine cannot rev up. Too much backpressure causes it to bog down. Again, then letting off the throttle it is much easier for the engine to breathe, so it starts to run normally as it spins down.
To test for a fuel problem you will need to install a gauge. To test for a plugged catalytic converter you will need to install a back pressure gauge in one of the oxygen sensor ports in the exhaust before the converter.