163K is nothing on a PSD as long as proper maintenance has been done. As with any vehicle with 163K the maintenance record is very important. If you have time I would sample the oil and send it to Blackstone, you can have this done in a couple days if you overnight the sample and pay a rush fee, also run a Oasis report through Ford and a Carfax report. Pull the intake and look for any dirt in the intake, oil is normal, a CCV Mod will cure this, but dirt is bad. Dirt is death to a diesel. Look at the fins on the turbo fan, if they are bent or chipped run away fast. If you open the air box and see a drop in K & N filter runaway faster. If the truck was chipped without at least a EGT gauge, laugh in the dudes face!!