So much hate on the Keihin PJ's. Nothing wrong with them, but they do take a bit of experience to get dialed in correctly. They are cheap, plentiful, and support motors that make decent power. If you have a motor with enough timing and compression to keep good bottom end, the PJ's are decent.
As far as Duncan, they quit doing R&D on banshees back when Jim Vidmar ran Pikes Peak for them. Even that motor was a bit goofy and only won because of a superior rider. There are far better fellas still actively pushing the boundaries of the little ol' 350 twin.