I don't think they made any significant changes. I bought one of the early models, and 6 new ones last year for a part time job. The only thing I noticed is that my engine squealed when turned it over by hand the first time. The others don't have as much pinch, imo. I've run 3 of the new ones, and I did notice one seems far and away more powerful than the others.

The high speed needle valve knob has a pressed pin as a stop instead of the original collar. I like this method better because that pin grinds down easily.