why is there oil in the turbo output air tubes going into the air intercooler?
The tube that directs the output high pressure air out of the turbo charger has oil drops and an oil film on the inside walls. It has built up a bit and has pooled a little in the connecter rubber boots that tie the tube to the intercooler.
Sounds like the turbo bearings are weak and need replacing. That's one of the possibilities.
Search Ford F-250 Super Duty Questions
Are you a UK consumer? CarGurus now has a discussion forum in the UK.
Ford F-250 Super Duty Experts