Ive been having the same starting issue for the past few years on my 97 but mostly when outside temp is above 60 degrees. First thoughts were fuel pressure, checked for leaking pressure regulator adding excess fuel, new plugs, performed pressurized injector cleaning. no help, I'm getting an average 18mpg. One night I left the truck inside the shop at my work, so it would stay warm, then pulled the plugs before starting and found at least three of them smelled of excess fuel, slightly damp. My guess is that I have some leaking injectors, and due to the temp, only affects a warm start. I have not replaced any due to the $100 + expense. thinking about sending them out to be bench tested and cleaned. Hope that helps a bit , I could use some ideas too