This past week the pulley on my belt tensioner broke. When the pulley broke the belt came off and the engine overheated immediately. The 'volts' light came on, on the dash and I saw the temperature gauge moving into the red zone. I was going 70 mph on the highway. I shifted into neutral and turned off the ignition and coasted off the exit ramp. When I went to the parts store to get a replacement part I was told that the plastic pulley that was on the car was superseded with a steel pulley because the plastic pulleys were prone to failure. I installed the steel pulley and everything was fine. I have driven it 500 miles since and I seemed to have avoided any permanent damage.
I noticed when making the repair that the supercharger belt has three similar plastic pulleys. So my question is; are these plastic pulleys something I should replace with steel before I have another failure and risk permanent engine damage?

If you wish to change them. Here is a link. There is a over sized and stock in metal

ZZ Performance

I had a similar problem with my supercharger pulley failing due to it being plastic. The thing just melted. Luckily the supercharger belt can be removed and the car can be driven except you don't have the additional power of the supercharger. I would replace all plastic with metal if available.

Many do change out to metal as it seems the better way to go. In the end unless that pulley has been in service for a lot of miles it'll have minimal wear on the surface. The bearing is the key to me though. Supposedly they use the same bearings in both metal and plastic pullies.

That being said, I hit up the local parts store and sourced all the pulleys in metal for my car. Including the ribbed one.

That sounds like good advice. I bought steel replacement pulleys but I can't figure out how to replace the smooth pulley right in front of the motor mount. Will I have to support the motor by another means and take the motor mount out to gain access?

i don't know but i'm having the same problem so if you figure it out please let me know cause the one your talking about did the same as your other idler pulley

The supercharger pulley also known as pulley #9 (there'* a picture where they are labeled) that sits behind the bracket is not fun the first time around.

You basically jack the motor a little, remove the ps pump to access the third bolt of the mount and remove the mount. Then you can change the pulley.