ISX 435 CM870 horrible MPG

[Hogleg]

Last tank, measured actual miles (502 miles) and topped off both tanks each time. Took 131.2 gallons. Shows 3.8 MPG. We run 2 lane roads at around 55 with towns every 10 miles or so. We run 70 miles each way loaded to 80K pulling an end dump. I would expect 6 mpg. Our Pete with a mechanical cummins ran 4.8 on this run.

Truck is new to us, bought in Feb. 695K on the clock. 2007 model, egr only. Had the computer read out when we bought it and truck averaged 6.8 over it's lifetime and 6.2 including idle. No red flags on report. Truck runs nice and smooth with no issues.

First thing I did was to replace the map and egr pressure sensors per this site. I have the egr differential sensor also but have not replaced it. Had not measured mileage prior to replacing the sensors.

No codes being set on the dash. I have the BT adapter and a cable (6 pin) but cannot get it to talk to the computer properly to read info with the cummins android app.

Is it possible I caused this with the sensor replacement? How should I diagnose this? I do not believe an overhead has been done on this truck.

Is there a reputable shop in Effingham that can be trusted?

John