I have a 97 Park Ave Ultra, which has so far been a great car! However recently the supercharger started making a squealing noise which was shortly followed by a LOUD growling noise but only when its taking in air. At idle I will only hear the squeal which I believe is the belt. As I accelerate the noise sounds like a loud growl and does not seem to coincide exactly with the engine rps as it gets louder and softer, which is what leads me to believe it is the supercharger. Its hard to directly monitor where the sound is coming from although im 90% sure its the supercharger, because I have to be driving to hear it... (also when making turns and out of direct air contact the noise stops) I changed the supercharger oil, which was DARK brown ... but it didn't help at all.... is the supercharger just dead?

Take the belt off the supercharger and turn the pulley back and forth. If there'* any play, the coupler is bad. If there'* play the tensioner will bounce a bit because the rotors are heavy. Check out this thread:

https://www.gmforum.com/normal-maintainence-138/change-supercharger-coupler-279064/

If your supercharger needs to be rebuilt, there are several members that have rebuilt ones they will sell you for a very reasonable cost.

Let us know what you find out.

A bad coupler sounds like a box of rocks. If the bearings are going it will make more of a clunking and or grinding noise. If you need a good supercharger, I have a M90 sitting on the shelf with good rotors, coupler and bearings. Swapping it out is easier then you may think.