Yeah having somewhere enclosed where you can wrench makes a big difference. The air flow capacity of an open element filter is good but the carb drawing in hot air from the engine bay isn't. If you cut the bridge out from the middle of the intake, then add an enclosed air box with a longer intake tract you will reclaim some torque. Funny that you mentioned side draft Webers - last night I was trawling through some of the old threads on carb options and quad rack bike cabs have been suggested. Cheaper than a pair of DCOE's, take up a lot less room and perform better.