We have a 12 winnebago aspect, I tow a 13 hyundai elantra. Care is just under 3000 lbs we dont carry a lot rv scales just 13000. I know the car is back there in the hills pretty much. went to flagstaff this past week and it struggled up the pull from black canyon and also mesa verde area. In denver it got down to 30 mph when we were there. Wolf creek pass a little more towards 45. I dont care for the electric throttle stuff but there is nothing that can be done.. The 5 star works pretty good civilizes the engine so that it just doesnt run away to 5000 rpm and lets ya have some throttle control. also help maintain shift points. Yes I would recommend one.
I would think anything heavier will be very noticeable with the 6.8. BP Diesel has a paddle kit that mounts on gear shift lever like the little sporty cars have, supposed to open up the trans to all its speeds vs the few on the stick. Might be interesting as the diesels have good reviews on them.. guess it mounts to the obd port which them takes away from monitoring stuff like a scan gage.