The new generation ASP 91 in the small case is a work of art. The carb is as good a quality as the Os in my opinion. If you have not seen, held or tore down one of these motors you cannot compare them to past models AT ALL!!!
I have a marine version and will tell you the port matching with the case is the best I have seen yet. The carb works like a dream. Mine is on a marine pipe and it will turn some rpms now. Best deal you can find. Look on Just Engines site and read the test replys on the engine.

Regards Curt