While I was replacing the supercharger belt and serpentine belt on my
Grand Prix, I tried spinning all of the pulleys by hand.

The serpentine belt tensioner pulley and the 3" supercharger idler
pulley didn't spin very easily as they should.

Rather than wait for them to seize up and destroy another belt, I
replaced them. Each pulley cost about $20.

I took pictures of the process and created a quick guide.

Here's the guide -
http://www.paulstravelpictures.com/GM-Pontiac-Grand-Prix-Idler-and-Tensioner-Pulley-Replacement-Guide/index.html

I hope someone finds it to be useful.

Cheers,
Paul Michaels
Ft. Lauderdale, FL