97 Sierra Backfiring

First post...Blew intake manifold gasket and took it to a shop for a repair.

Mechanic called and said the two screws in the distributor rotor were just bouncing around inside so I said replace it.

got the truck back and it is backfiring through the intake and running crappy at about 2500 rpm .

I took the distributor cap off and the rotor turns maybe an 1/8'' each way could it be the distributor ?

Replace the distributor. Your worm gear is worn.

You can also replace just the gear. It's not that expensive, and the dealer has it on hand more than likely. I did this a year ago on a 98 (5.7L), and cleared up the problem. The gear was so bad you could cut paper with it. The teeth were just on the edge of breaking.