I'm a 7.3L guy myself, but my dad has a 6.0L 4WD with a K&N cold box and a Magnaflow 4". He's running a Hypertech Power Programmer III and has been for years. His problem is recently when towing in hills with a fairly heavy load (37' 5th wheel camper) his truck will downshift. When this happens he starts blowing out coolant at an insane rate. He had a pressure test done on the cooling system and everything maintained pressure as it should. Any suggestions or places to look next woud be helpful. Thanks to all of you in advance.