My DS would do that same thing if I would be going down a hill and using the engine braking. Then, when I would give it gas at the bottom, it would backfire into the airbox and take off or sometimes stall. I talked to the district rep (he happened to be at a poker run I was at). He suggested turning the air/fuel screw an 1/8 turn out. He stated they are EPA lean from the factory. No more problems for me.

 

Uglyman32, that's the one.