The (audio) line outs from the EWI need to be connected to a "Line_level" input on the iRig. That maybe the "Instrument Input" but I am not sure.
Some-else may join this thread to comment.
Or, please raise a Support Ticket, here:
http://www.ikmultimedia.com/contact-support/mi/
for some one to one advice (US (East Coast) Business hours, generally).
I see in the EWI User Guide that there is a wireless connection. Maybe you can use that?