Im new to diesels and this forum too. I had a very similar experience. Bought the truck 1989 f250 w 7.3 non turbo in Chino cal and that night drove to las vegas for work. No ***** what so ever up grades and temp went from 180 to 220 up the long grades and oil pressure from 40 to 60. Blowing smoke the whole time. My switch for my dual tanks stoped working and a couple days later the truck died on me on the freeway. I guess my gas guage lies and says it has a quarter tank when it doesn't. The fuel switch valve/ assembly was shot and i got an air pocket in the lines somewhere so they had to bleed injectors and refill fuel filter and replace whole fuel valve assembly. They showed me the old assembly and it was trashed. These trucks dont switch electronically its mechanical. The Throttle position sensor went out the day I got there btw so it was in the shop right after I bought it. Also the alternator was very bad and truck wouldnt start so I replaced that. Honestly have the electronics tested batteries, alternator, connectors etc. BTW the fuel valve assembly is a $220 part and is a Ford part and the TPS is about a $50 part. From what little i know about these old irons we purchased they will tow anything anywhere they just take a while to get there. I got 18mpg hand calculated on the way out there to vegas going up and down grades. Banks turbo upgrade is in the near future i hear its a must.