I have a 01 Dakota with a 3.9 with a standard 5spd. It's been a great truck. Always up kept. It has 211k miles. 75% have been long distant miles. Well around 196k the truck started acting up. I would be driving down the interstate and at the time if I was going faster than 75 mph it would bogg down and slow 2 - 5 mph then pick back up. It did it regardless with cruise of not. Well obviously it has been getting worse. I've put a new fuel pump and filter inn and it helped for the first 15 miles then it started doing it again but, now it will back fire occasionally but only ar highway speeds. And it will bogg down and back fire horrific at any sort of incline. So I put a new Cap, Rotor, pickup coil, plugs and wires and a new throttle positioning sensor. I also went to my exhaust man and my converters ate excellent and my vacuum hoses are in good shape too. Well it all helped but after 5 miles it started acting up again and worse. Now when I shift from 3rd to 4th and then to 5th it'll hesitate like hell and bogg down unless I floor it. And this is odd. You know that on a standard it gives you a shift light when to shift gears well it flashes to shift gears when I'm already in 5th...lol. So now I've replaced my map sensor and it just worsen my back firing issues. So I put the old one back on and cleaned my throttle body real good and took out and cleaned my air idle control valve. She ran really crappy after that but a few days went by and now surprisingly she's running better. But she still boggs and back fires up hills but on a straight run she excellent now. I'm still puzzled on what's going on with my truck. Any suggestions? Thank you John