bearing check.....
To check the bearings in the Supercharger all you need is a 12" extension from a socket set, I use a 1/2", and place it on the nose cone while the engine is running. Put your ear to the end of the extension that isn't on the nosecone, and listen to it. If it sounds very rough, then chances are that the nosecone bearing is going bad. Repeat the process with the other 4 bearings that are in the charger. 2 up front (near each of the corners of the housing behind the nosecone) and 2 at the back in the same location as the fronts.
Either that or take it to a mechanic that works on Diesel engines, they usually have a lot of experience with Turbo's and Superchargers, and ask them their opinion.