I installed a bd #8 plate on the 12th and spent the last week "tuning on it". I have gotten to a point that empty i can see 1250 deg accelerating up about 4% grade lasting about3/4 mile. now this morning (52 deg.) I hook on the the trailer and wood maybe 6000lbs and run up a smaller grade wfo for about 1/4 mabe 1/2 mile and it will not go over 1100 deg. fyi I've got the boost backed down to 28psi. so does this make sense. empty hot-loaded cool?

 

How cold was it when you were empty and tuning it?? Your sig says your in colorado and I know temps can vary,but it does sound strange , was the boost set down before the load? Goodluck Rick

 

boost mostly around 28 to 35. so not much variance there, however coming home from work at night between 45 and as low as 30 deg? now go figure?