Go to Colorado Diesel down in Castlerock. They are extremely awesome to deal with.
I would highly reccomend leaving the comp off and make sure you get your truck to smoke as little as possible.
With my DD2's and [censored] in the low fuel position, I only saw an opacity level of 10. Which I felt was kind of high.
Let me know if you have any questions, I'd be more then happy to help out.
Kev