500 hp efi ?
 

engine won't idle. give the least bit of fuel and runs fine.
please help.

IAC Idle Air Controller or idle adjustment

You need to hook it up to a code reader.

on vacation can i take it out and clean

Its a sensor, and if its bad, its bad.

Temporary fix may be to extend your throttle cable to keep your throttle body/blade open a tad more than usual to get you through vacation, but you really need to hook it up to a scanner. A Merc dealer can help.

If you adjust the idle; do it ONLY enough to keep it running. Make sure your idle is around 750rpm. Any more than that will damage your drive while shifting.

IAC is a gear driven, reversible linear motor with a pintle valve on the end of it. It is not a "sensor" . It is screwed into the throttle body. It can be removed and replaced with a factory GM unit( which it is anyways). Carbon build up in the throttle bore can cause a no idle condition as well as it supplies a fixed amount of idle air( minimum air rate).