the fast idle valve would explain the jumping rpms on startup. i had mine changed not too long ago. in cold weather, it would feel like someone was stepping on the gas with the rpms dancing between 1500-2000K. in warm weather, the rpms would dip really low then spike between 400-600.

the engine stalling could be caused by a jammed EGR valve. i went through that too. my rpms would dip around 200 at a complete stop, then die.