So we just did a egr block off plate and 4" dp back on an 08 LMM as well as a S&B intake and put farmtuned tunes on it and pulled an inclosed closed trailer 600 miles and I lost 4mpgs after doing so, as anybody else ran into this problem??

 

How does the truck drive is it smokey? Have you called your tuner to discuss this issue? As far as MPG were you hand calculating the mileage prior to deletes? Are the numbers you see now hand calculated? Is your speedometer actuate to the vehicle speed?