My Disco has 199,617 miles on it & still going strong.
Oil in pipe from turbo is normal on tdi's, as long as it's not excessive. The engines gonna slightly worn at 135K miles :roll: :lol:
Check the engines not breathing heavy, put your hand over the oil filler cap, cap removed, there should be a slight suction. If it is breathing heavy your hand will try to be blow away from filler.
On the air filter casing there is a smaller braided pipe that runs to the drivers side of the engine into a black plastic oil strainer, bolted to the rocker case.
Take that off & give it a good clean in parrafin. It would be worth cleaning the inlet pipes & intercooler too as mentioned.
Check tappets.
Be worth changing air, fuel & oil filters, & oil.
If the engine is ok then it would be worth putting a good quality injector cleaner or having the injectors reconned.
Check that your throttle cable hasn't stretched. Hold throttle flat to floor, engine off, & ensure it is hitting stops on pump.
Use a good quality fuel...not supermarket own!