x2 on the vac leaks. check around the blower casing and check all the plastic vac lines. are you still getting problems with your evap purging? it definitely shouldn't be purging on start up, and that would be an "internal" vac leak. do you have access to a scan tool that would tell you purge flow rate or fuel trims?
and yes, there is an idle relearn process. i recently replaced a throttle body on a newer tahoe and before it relearned position it would idle at almost 2000rpms. no fluctuation though, but its worth a shot. you can command it with a tech2 or other scan tool, or you might be able to let it idle for a few minutes and the pcm will relearn on its own
