Don't know about the EWI USB, but if it's a MIDI controller (must be a MIDI keyboard if it's like a Yamaha WX5), then no problem at all to communicate with Max.
I would recommend that you download the EWI's manual to be aware of the specifics.
I don't knwo if i'm on a good topic but I've problems with my EWI.
I want to control Reason 7 with my EWI, with the pitch bend include in the machine. But with the patch below I have an error message :
"queue stepped on itself"
I don't understand why, because Reason don't send informations to Max. When I launch the audio, the message "queue stepped on itself" stop !
Is someone can help me ?