Hi everyone. Long time lurker, first time posting.
I have had my M715 for a few years now yet rarely drive it. This summer I decided to do something about it. But each time I drive it the engine burns lean, starts to backfire, miss, and even dies. I'm sure this is more a general engine issue rather than specific to our trucks but since this is the only carb engine I own I am soliciting here.

Problem solving steps I've taken:
Electric fuel pump installed on frame near tank. Cleaned tank (professionally), rebuilt carb (professionally). I've verified that the electric fuel pump is supplying sufficiently, and now that I've had the carb rebuilt I am at a loss.
Engine runs fine, rev's fine in neutral, but within 2 blocks of driving... goes lean and dies.

I'm out of ideas on what to check?
Thanks for anyone's random thoughts.