Why would my 1989 420 Mercedes stall on the freeway or upon acceleration? on 1990 Mercedes-Benz 420SEL

The fuel sensor in the "dash" area has been swapped. It's had a tune up.I happens after idle sometimes but also on the freeway. Very intermittent>

Asked by for the 1990 Mercedes-Benz 420SEL
have u changed the fuel filter, its the big round unit that sits at the rear passenger side of the car with the twin fuel pumps, it has a black plastic cover over the fuel pump assembly