Stalling and backfiring

My SUV stalls all of the time it backfires every now and then. Sometimes I have to crank it 2 or 3 times before it starts. It has a very low idle and when you get to 50 MPH or more it starts to hunch. I have to let off the gas and then get back on it and one day on the highway I was stopped at a red light and when I pressed on the gas it was stuck at a low idle and would not get past 20 MPH along a 10 mile. I route I managed to get it to 40 MPH in a 65 MPH speed limit zone. I stopped turned it off and pressed the red fuel line switch in the back and it was fine for about 2 miles then it started hunching again but didn't lose power. I had to drive it 8 miles down the road before all of this to my mechanic with no catalytic converters and it ran just fine. I have unplugged the MAF sensor and the o2 sensor and that didn't fix it I couldn't even get out of my driveway.

I also had AutoZone put it on a machine and it popped up o2 sensor but it's unplugged and it doesn't explain all of the problems.