Does it sound like a metal shovel being dragged along a concrete driveway? If it only does it when it is cold then it is the IAC in the TB...its loud...and normal. The SLP Air Box on my mom's '03 L36 LeSabre is louder than crap at idle (and yeah...I put a SLP box on it...I know...awesome)...when it warms up...no more sound.