Greg, I had a similar problem where my gas assist was kinda popping and poofing intermittently. I ran the problem by the message boards, and got some good advice to clean the burner assembly. Specifically, a brass part before the gas gets delivered into the kettle. It is a place where the gas mixes with the air, and the advice was to disassemble the parts (held together with a metal clip, if my memory serves), then use a wire brush to clean the face of the brass piece and to run a piece of the wire brush directly into the pinhole in the center of the brass piece to clean that out.
I did all of that, and the thing now runs like a champ.