I put a smaller pulley on my supercharger (yeah, bring the flaming).
After that I heard noises in the exhaust when at certain rpm, also going down hill (no ignition). So I figured it could be the catalytic converter falling into bits and getting shot out the back.

Today I took a look, and it's completely empty!

Is this "normal"? I'm putting in a cat replacement anyway.

I don't think the noise is the motor pinging, since it happens when I'm going down hill and braking on the gear / motor.

 

Guess not