need some info, 1998.5 2500 4x4 all stock except for fass, I drove to denver and back today and the truck ran well , good and strong going uphill but going downhill it would studder and blue smoke out the tailpipe I check my fuel milage and I got 17.5 mpg going over. I am hoping it not the vp44, I checked for codes and there is none. I used a obd2 to check codes.