I also have this POS 730N system.
Pulling my fiver I routed a trip to Zion NP in Utah, camping destination in Virgin, UT. I had the option checked to avoid tunnels since I know there is a tunnel in the park that I am oversized for. The system simply replied to me there is a tunnel on the route and no other route is possible.
Here is what really is happening... The 730N simply found no other route because the correct route goes from the Utah map to the Arizona map. From Kanab, UT the 730N wants to route to the north to UT-9 which is the NP road with the tunnel. The route to take to avoid the tunnel is to head south from Kanab into AZ to AZ 389 going through Colorado City, AZ to Hurricane, UT. I knew this from looking at a map myself. Shouldn't a nav system do this for me? This alt route was not even on the list of optional alt routes. Simply was not aware of this other route.