Have you figured out what the cause of your problem? I am currently experiencing a similar issue with my 1990 7.4 tbi. seems to only misfire, bog, choke, sputter, and lack power after running for more than 10 minutes, and seems to be worse when its hot outside, and also only seems to do it in 2nd or 3rd gear. Runs fine in park. The block and heads were completely rebuilt recently, but most all of the other parts were put back on the engine, with the exception of: new distributor, coil, plugs, wires, new coolant temp sensor, new water pump and radiator. All of this was done at a local trusted shop. My next attemp at fixing this issue will be replacing the EGR valve and solenoid and then a new map sensor. It has no cats, and occasionally throws a lean or rich code. Any advice or ideas welcome.