up to about 60-65 hp is ok for towing if you take it easy. Most programmers towing tune is about 40 hp, so 50 hp should be their version of the tow tune. Normally the second tune is for fuel economy and for towing light....say under 6000 lbs. As far as limp mode, it normally happens during the 4-5th or 5-4th shift. It happens to save the tranny. Just don't have high horsepower settings and do WOT shifts during those two. Just ease into the throttle. The limp mode will lock out 5th and you will only be able to run 2000 rpms in 4th until you pull over and shut the truck off and restart. It is a good idea to keep the programmer in the truck so you can read codes and clear the check engine light.