Duramax or Powerstroke

Klutchdust, since you already own a Dmax and are towing fairly heavy loads and probably towing through mountains, I would forget a stock gasser. Doesn't matter if you are retired and in no hurry, towing a heavy load through the higher elevations with a stock, non tuned gas engine would scare the bejessers out of me. I am towing close to 10,000# with my Ford 6.4 and drive through Kansas, Colorado and Utah. When you get west of Salina KS you go up hill both ways, then you have the mountains in Colorado and Utah and those are extremely difficult climbs with a tow load even for a stock diesel. Just because you flash a CPU with a performance tune doesn't always make the rig go faster. I do it for better fuel economy and much improved pulling power, ie: mopower. I recently installed an aFe Cold Air Induction System on my 6.4L and had an immediate improvement in mpg to the point where the modification paid for itself on my first trip out west. More power always equals more mpg. Its simple physics. More power also means less stress on the engine at typical operating conditions.