I have a 99 F350 4x4 7.3L v8 with 409,133 miles. Recently I started to have a small loss in cabin pressure, low pressure if engine is cool but would fix itself once the engine was warm usually about about 3-4 mins after starting to drive. Now I have almost no pressure and the truck will shudder hard and stall and barely move, and continue to do this tell the engine is very warm and has been running about 30-45 mins. I can hear the pump engage when I turn the key before starting. I checked the bowl and it's full of fuel and has brand new filter, checked the lines to the pump and no leaks. The only other thing I can think of would be the injectors or the relay or 1 of the fuses but I've never had a relay or fuse cut in and out before, they either work or they don't. Any suggestions I am at a loss. Thanks in advance..... This issue only happens for the 1st 30-45 mins of turning over but then runs like a champ with no issues after the engine is nice and warm??????