1994 Dodge Ram P.U. stalls, oil light comes on, will start

Good day to you. My pickup stalls , sometimes at the light, sometimes on the high way, to the point i cant drive it. some times it stalls, oil light comes on, RPM dies, then out of no where RPMs kick in, and its fine. other times it stalls and stays off, with oil light on. Hope you can give my good answer. my mechanic has replaced coil, wires, plugs,and the computer.