I've got an 04 3500 QCLD SRW, auto trans, 4X4. The only mod I'm sure of is the Banks 4" stainless exhaust, no cat, and an AFE stock replacement air filter. Last trip it got around 17.5 mpg, hand calculated. I tried adding the ashless 2 stroke oil in the last tank and got 19 mpg hand calculated. I must admit, I don't like the smell of the exhaust with the 2 stroke oil, but I like the milage.
I'm tight on cash right now(who isn't) the storm that totalled my 97 12 valve destroyed alot of other things and I was in the middle of a whole house remodel when that happened. You get the point.
Upgrades are going to be budget minded with an emphasis on fuel milage. I don't haul on a regular basis any more, but still average pulls around 8000-10,000lbs. I have a 150 mile round trip to work and back, but I only work 10 days a month, I work 24 hr. shifts.
I was thinking that seeing as my exhaust flows better, I should help it breathe better. Thinking of going the BHAF route and making an aluminum heat shield. Something along the lines of what usmcbay did over on the 5.9 cr bombs side. 4" dia. with a paper filter and a cover.
After that not as sure, thinking about an Air Dog 150 and a Smarty Jr.
Also plan on trying one of BG's fuel lube additives in place of the 2 stroke oil.
What are your opinions/suggestions?