I am having the same problems currently after a trubo replacement on my wifes 1991 350sdl. It started after a trubo replacement and an oil change. It would not build oil pressure at all. Replaced the orings and now the pressure is low and dropps to o when accelerating. Once you are at speed it comes up to 1.5-2 ...some times up to 3 like it used too. What was the fix for your car? . where is the oil pressure sending unit? I hooked a manuel gauge to what apperared to be a sending unit on the bottom of the oil filter housing. It read 15 psi at idle and up to 80 at speed. but the dash gauge also read , so this was not the sending unit for the oil pressure gauge.
Does anyone have any ideas, any help or similar problem on another model.
Thanks