Is your car pre- or post facelift?
Pre facelift has a magnetic clutch which engages the supercharger at around 2000 rpm if there is no load on the engine (revving in neutral). With load on engine (ie in drive) the clutch engages much sooner (less than 1000 rpm)
The post facelift has no clutch on the supercharger which is hence always engaged.
My 2001 is post facelift (vin=1F202536) and there is no clutch on the SC pulley. It is bolted right to the end of the SC shaft. Check out the end of the pulley. I don't think you'll find a clutch there. That's the best way to find out if it is running all the time or not.