[ngoma]

Surprised it would even start/idle.

Good question: Why would that tab break off?

I had a similar, where the "lobster claw" that encages the long spring broke. I figured it was due to my previously replacing the IP top cover gasket and not quite getting the mechanism positioned correctly when replacing the top cover. That is a tricky one. The Dodge/Cummins version of the Bosch VE IP has a much simplified throttle arm mechanism.