Since I basically just got this car, i've been going through things and making sure everything is good.
One of the first things i saw was an idler fragment on the subframe and a belt fragment tucked in near the coolant elbow.. so i picked up a pair of Gates Green Stripe belts.
As I was swapping them in today, I discovered the SC pulley and crank pulley for SC were both packed with rubber and cords in the grooves.
SC pulley is easy enough to clean with a knife blade but the crank pulley is harder to get to with the wheels on the ground so that will have to wait.
But the test drive afterward was more fun than normal, I can hear the supercharger whining harder than it did before, and it is pulling harder than it was, so it had to have been slipping.
positive result