Hi my ecm went out on my 2002 duramax LB7.i sent it in to so cal diesel. The guys there were very nice but I didn't want to burden them with my 21 ?s.lol I thought I would take it to the forums.so he Said there is a light , economy, and heavy tow tune and can program it into my new ecm.my truck is a welding rig loaded with about 3000 lbs.which one should I get? What are the characteristics of the three? whats The difference in mpg, torque, and horse power.can it still pass smog iam in cali.are they hard on the engine and tranny? I don't plan on doing any upgrades except for efi live.thanks .