Yep, When it stalls, get out and open the gas cap.
If it sucks a bunch of air in and you hear the tank pop back out that is the problem. Years ago I walked to town gas can in hand a couple of times before I figured that one out.
If that isn't it check for kinks in the fuel line and make sure that all of the brass fittings are the correct internal size. Once in a while you can get ahold of a fitting that has the correct threads/connection types but it has a very small orfice in the middle. That would be Idles fine, smooth low speeds fine, full throttle, falls on it's face when the float bowl runs dry.
