As said, check filters and so forth first. After doing that, my M35A2 would still not get out of it's own way. I found that the military had turned the fuel injection down significantly. I installed a pyrometer and boost gauge (very important to prevent melting pistons!) Then I turned up the fuel following the instructions on this site. I limited my exhaust temps to just 1050 degrees, when pulling a long hill, with a full load. Now I have a great running truck. Good Luck with your machine. By the way, I also installed a remote, transparent, brake reservoir in the cab corner to the rear of the drivers door. It gives you a clean way to add brake fluid and you can see your level overtime you climb into the cab!