My supercharger started to rattle at an idle and I know that its a common symptom for the coupler going out. I already had a new one so I put it in and I still have a rattle noise at idle. I pulled the sc belt and started it just to make sure thats where it was comming from and it was quiet I also checked the idler and tensioner pully. It sounds like the noise is comming from the snout but when I had it apart I couldnt feal any slop in it. Any ideas on what I should do next? The car runs great it has 250,000 miles on it but its always been maintained / tuned up.

2000 Bonneville SSEI

Could be the bearings in the back side of the rotors.

I need to take the sc off to change out the lower intake gaskets anyway so do they sell a kit for it or should I wait to see what parts are worn out whan I get it off?

I'd probably wait until you got it off. But you did say you didn't see any slop in the snout bearings correct?
If not, only other possibility is the coupler or the needle bearings in the rear. ZZPerformance has the bearings you need...
Eaton - EATON Case Needle Bearings #ETN-CNB

I think you need to replace the coupler. I had to replace one years ago on my old GTP.

CNC Machined Supercharger Coupler

The supercharger on my 94 SSEI started rattling and I got a cheep replacement out of the junk yard but this was about 10 years ago.

I replaced the coupler first cause I already had one on hand with no improvement. I couldnt get any slop out of the snout at all everything was tight but its weird that the rattle sounds like its comming from the outer bearing at the pully but I guess the sound can travel through the sc.

My friend has a sc off of a 98 Buick would that be a m90 or a 62 and it'* been off the engin for 5 years is there anything to be concerned with from it being off for that long?

M90. M62'* were on the Series 1 engines.

Just as long as there is oil in it and the rotors spin freely.

Yea I guess that would be a better question would a 98 be a series 1 or a series 2?