Im guessing if you hear some weird vibrations and sounds, it could be letting go, as long as it had the newer steel washers. If its ceramic, its an immediate catastrophic failure. If the SC is letting go, the engine can still run, but the SC isn't really spooling to make boost and through the timing off on the engines, which would probably make some terrible noise as the RPMs go up. Definitely don't want to keep running if you think the SC is slipping.
One method to test if the SC let go is if your engine is idling, try to squeeze the outlet hose of the SC. If you can't depress it, you're making boost. If you can, it let go.
Other things that can make noise are spark plugs, especially if they haven't been changed in a while or fouled up. One of my engines had a foul spark plug and low oil pressure. When I ran both the engines, the one with the bad plug would vibrate harsher and sounded more like a lawnmower. Wouldn't hurt to check plugs first before pulling your SC out.