Just curious what settings are you running your Smarty on to see great mileage like that?
I have the JR with 67ME software set on performance with POD on 99%, Torque on 4, and timing on 4. I dont load the truck up on these numbers. I carry about 1K of extras in the truck. When I tow anything more than a riding mower I back the torque and timing back down to default to avoid any trouble. I cant say for sure but it seems to get better mileage with the exhaust brake off, just an observation that I havent proven yet.