1985 300TD Wagon

[BigRed0803]

I just got a 85 300 wagon. I am having problems with fuel delivery I suspect. When driving the car around town or on short trips everything is fine but when taking a long trip after a while the car will just start losing power. It is so bad I have to pull over. I can turn the car off and let it sit for a minute or two and the car will do fine for another couple miles or so til this happens again. This turns a 2 hour trip into a half a day journey. I have changed both fuel filters and have also cleaned the tank strainer. I bought the car thinking one of those things would take care of the problem but it did not and now I am stuck with the car. Does anyone have any idea what could be causing this? Thanks