poor fuel mileage
 

I replaced a 2003 ho cummins ( spun rod bearing 184.000 km ) with a 2006 cummins (126,000 km) Fuel mileage went from 23 mpg to 18 mpg empty and went from 13.5 to 9 towing. Dealer says that the injectors need to be changed to 2003 injectors and the fuel injection shop claims that the ecm controls the amount of fuel the engine requires and that the 2006 injectors should be fine for that engine. The ecm is off the 2003 engine. Anybody out there have any ideas for me.