The throwout bearing will make a whining/scraping noise if gone bad. They also tend to squeel when the clutch is being engaged. If you're hearing a constant rattle it idle, I'd say that your flywheel is starting to go. Higher mile MKIV flywheels tend to rattle at idle.
Does your can have problems shifting? When my pilot bearing went bad, shifting became more difficult. The bearing would only make a high pitched sound when the clutch pedal was depressed all the way while idl/.
I bet its not your throwout bearing. When they go bad, they squel when engaged in gear and in the middle of the clutch travel if you have a push type clutch.