Annoying rattle at idle

[Redcallen]

Two things:
1. Whats the normal idle rpm for our cars?
2. When my car idles (700rpm), i get this loud annoying rattle coming from underneath the car. I listened outside of the car and it sounds like its coming from somewhere behind the right front wheel. Its a metal rattle with a little squeak. If I rev the engine, the rattle stops right before it hits 1K. Weather definitely has an effect on it. the colder the weather the worse the rattle. it virtually disappears in the summer. I've checked all known clearance issues, so i'm trying to get a list of other things to check. Thanks in advance.
Mods: SLS J-mid pipe catless, magnaflow catback, motor mount inserts all around, bronzoil shifter bushings, Injen CAI

 

[FlyinHawaiian]

My car squeaks sometimes too at those RPMs. The car typically idles around 600-800 RPM. I think the squeak is probably the exhaust rattling. Check all the fittings on it and make sure everything is tight. When its warmer out, all the parts tighten up and fit better; just the nature of the beast.

My car's name is 'Buzzy' for a reason!