Pressing the accelerator pedal during start does nothing more than exercise your leg. The fuel for start is controlled by the computer and the accelerator only becomes active after start. The acclerator controls a rheostat (basically) which makes electrical inputs to the throttle position sensor.
What you are describing is seems to be normal starting. When the engine is hot the fuel vaporizes and it is not always the correct temp to provide the best fuel/air mixture for start therefore it takes a tad more fuel added by a slightly longer crank cycle to have the right combustion mixture.
Tom
TBC<br />2001 2500HD Duramax Ext cab short bed, Indigo blue, LS with leather; Edge Juice ver 4.61; 42 gal fuel tank toolbox combo, black Westin nerf bars, K&N Charger filter, Fumoto Drain Valve, GM underseat storage, Sirius Satellite Radio.