[bnorth]

Gorgeous truck and it could be any number of things but it is likely tune related. I would find a reputable shop in your area that specializes in ecm tuning and knows GM factory ecms and software (likely HP tuners) well and have them go through it. A good tuner can look at the tune in the truck and see issues and then make corrections while street tuning but may want to fine tune on the dyno. It may have been tuned by an amateur that got to a dyno number and said good enough but left a lot on the table as far as drivability.