I bought a project DR350 recently and pulled this high-flow aluminum airbox off of it. It is exceptionally well-constructed, perfect stack-of-dimes welds, Dzus fasteners...it's really a piece of art but it's not marked. Can anyone tell me who made/makes it?
Kientech used to sell an aluminum airbox for the DR350 called the vortex. Some say it works great, others said no difference in performance. It was designed to work with the dirt model "pumper" carb.
Jesse Keintz sold and still sells (I believe) an airbox like that. IIRC you do have to retune your bike to take advantage of it. He knows his stuff. There were a few others who sold something similar.