I bought an '04 S brand new that I kept completely stock for the 3 years I owned it. I have recently been looking at a 2005 S with 130k miles. There aren't many records with the car. However it seems as though this car has more power than the one I owned new, so I'm wondering if the pulley has been changed. Is there a good way to tell if it has?

 

Just look at the pulley it will have bolts in it if it's aftermarket.

 

OEM is pressed on. Will have a plastic plug in the center covering the SC shaft.
One thing that can make the facelift cars feel more powerful is that they have lower gearing. My friend's stock '06 feels stronger than my pullied '04.

 

The supercharger pulley is the one just to the left of the circled bolt:




This is what the stock one looks like. Aftermarket ones are usually silver.

 

Thanks for the help everyone! It's been 9 years since I had one of these cars so I've forgotten a lot of the things I used to know.

 

We have some good images of the stock and aftermarket pulley in this article HERE that may help you visually. Figure 27 gives you a good image of an aftermarket one installed and figure 19 is the stock one. Good luck with the purchase!

 

Those images were great to use as reference. Based on the tips and pics provided, the car in question does not have an aftermarket pulley on it.