UMP makes a Class 11 specific air box.

Is it worth the $135??

Or just find some other way to route the carb to the 4\" UMP air filter :D

one of these thingies, not the actual air filter

We used a regular ABS elbow for the first year. The Class 11 UMP box has the velocity stack inside it, that had a better stand off air flow and did help with acceleration from a stop, without a lag to catch up. Weather its worth the price? can't say. Just went with what everone else was running.