This week while I was off, I was going to start some rust repair on my Trabant but ended up trying to figure out what was wrong with my Fiat Spider. It as a Garrett T3 sourced from a Volvo 240. I originally thought it was engine knock but think it's the turbo itself. I'm trying to determine if the pivot mechanism on the wastegate is worn and is causing the wastegate to rapidly open and close causing this ticking sound. I Googled "turbocharged rattle" and all sorts of videos popped up on this subject.