I work in an underground mine, and the problem with these 6.6 liter engines is they produce way to much co2. What could be causing this or is there something i can do to trick the computer. Iwas thinking of resisters in the map sensor wiring to beleive the truck would be running on surface instead of under ground to cut back fueling.. Does anyone have any sugestions

Very high co2? That just means you have an efficient engine.Are you talking about CO?

You could have the VE table altered to run a little leaner...but you can't go too far. At idle or very low load it wouldn't be an issue.