If it was my 2.8 I would be thinking...
Fuel filter (done that)
Youve done the Air filter (but then I wouldnt have even looked at that in the first place)
Fuel lines from the tank to the pump (outside chance but hey ho... they do rot out)
Vac pipes
Fuel tank breather
Fuel pick up in the tank (the 2.8 one has a little rubber thing that acts as a non-return valve)
Loose wire in the ECU (yeah, I know the 2.8 doesnt have a ECU, but I think the 2.5 does?)
This posting may have been helpfull, on the other hand probably not... Either way, I may have had drink when posting it in which case it's probably not as helpfull as it could have been
Work safe, and remember all technical problems can be resolved with a hammer, the trick is knowing where to hit it and how big a hammer to use (I often find it may also help to have a spare bit in the shed to replace the bit you have just mullered

)
Work in Progress (or not as the case may be) I give you....
'O-no' the truck.Comments on 'O-no' the truck may be left
hereWork in Progress (or not as the case may be) I give you....
'Truck'Comments on 'Truck' the truck may be left
hereOwning a 2.8 is a hobby in it's self...