Thank you for you time..
I have recently purchased a used 2005 Ford 6.0 diesel turbo. Was running fine then all of a sudden the truck became sluggish and registered no turbo pressure or pressure sometimes. A well respected local mechanic told me that he believed it was due to a bad sensor. I don't know the name of the part but it is roughly 6 inches long and tubular looking and very expensive $395.00. 5 days later and several of these parts later I was told that the truck keeps "Blowing" this sensor. He then told me that when he checked the oil, "it was the wrong type for a diesel engine"?? He changed the oil and voilà the problem was fixed.. so he thought. On the way home from the shop, at about a consistent 50 - 55 mph, the problem again reared its ugly head so now the truck is heading back to the shop. I trust this guy but I would like to ask if any one else might know what could be going on so I am not total ignorant.

Thanks again