I've got a 2003 F-250 with the 7.3. On cold starts, regardless of outside air temperature, I have to allow the engine temp to come up to normal operating temp for it to perform normally. If I crank it and take off, it does good up to about 30 mph then starts to miss and vibrate extremely hard. If I feather the throttle, it will ease back up and run fairly smooth until the temp comes up while driving. Problem appears to be getting worse as it is becoming increasingly hard to start. No check engine light, no smoke, no clue. Replaced the fuel filter and air filter... glow plug relay next with my fingers crossed. Any help would be greatly appreciated... please be detailed as I am still diesel ignorant and have no clue what most of the shorthand on here means.:dunno: