Fuel Consumption GQ 2.8TD

Hi All,
Seems that my Patrol, (141K manual 2.8 TD) , bought new in 97, has recently been getting poor fuel economy. I was averaging around 25 mpg but now am averaging about 19mpg, nothing else has changed, still got the roof racks, drawers etc. It still has the same amount of power (Not much down low enought over 1800rpm) but just extra fuel going in. Does this mean I need to get the injectors cleaned???? My mechanic has suggested a diesel pump tune I think it was ( acouplea years ago). I have a 2.5 inch exhaust dump pipe back and am happy with the truck. Please no comments about 4.2 engines. I've read them all.
Cheers
Steve