Try a new Sending unit......you can get em at any Autoparts store , not too expensive...
40-50 psi at high speeds is pretty "normal"...for oil pressure.
No less than 25-30psi at idle.
Vacuum leak could also be a bad intake manifold gasket, bad PCV valve, if it hangs open it will cause a vacuum leak... cause your engine to stall and die...
Just some ideas...."BH"
07-JKU-X /Poison spider Evap.Skid/Master craft grab handles/Or-Fab spare tire-can carrier/ Gibson SS Duals/ Q-tec Floor Liners/Hidden Hitch Receiver/ AntennaX 7inch/ 48" Hi-Lift./ 8"X16"X4"bs Steel smoothie wheels/ 265X75R-16 Kelly Safari TSR tarz.
Viet Nam Veteran 69-70, Troop "D" (AIR) 3/4 Cav. ,25th Inf. Div. CUCHI RVN. UH-1H Crew Chief of the "Pinball Wizard" 68-16224. Call Sign "CENTAUR".