It may be your Throttle Body gasket. I did some searching here http://www.automotiveforums.com/vbulletin/index.php and came up with this. My 95 Tahoe surges a little at idle. They said to spray carb cleaner around the base of the TBI and see if the engine speeds up. You could be in a situation where the gasket seals a little better when warm. I doubt you have a fuel delivery problem. My experience with pumps is they are fine or dead. And you seem to have plenty of power when warmed up. You might need slightly more fuel when cold, but nothing compared to high speeds under load.