97 f250 w/325k mi. runs fine until I throttle past 3/4 then totally loses power until rough idle for 1 or 2 min. at which time it smooths out and will run fine until throttling past about 3/4 again. Acts like fuel starvation. All new filters and oil. Have heard maybe fuel or injector pump or fuel tanks (has dual tanks) problem same using either tank.

Assuming you have recently replaced the under frame fuel filter, I suspect the fuel pump is worn and showing its age. I would replace the fuel pump (Motorcraft only), before replacing the injector pump. I would focus on the injector pump next, assuming the turbo is fine.