A couple of months ago I posted some questions about going into limp mode while towing a 10K lb RV on a hot day. After installing a Kennedy lift pump I towed that same rv today and I think the problem is solved. I positioned myself at bottom of long hill and stood on the accel towing that rv and it went on up, no limp mode. I'm guessing the problem was soft fuel hose collapsing but I'll never know since it could have been water in fuel etc. lift pump is a good idea anyway.