Where is the fuel pressure testing port on 91' s-10 4.3?

On a 1991 Chevrolet S-10 with a 4.3L engine, the fuel pressure testing port is located on the fuel rail, near the throttle body. It typically has a Schrader valve similar to a tire valve, which allows you to attach a fuel pressure gauge. Be sure to relieve the fuel system pressure before attempting to connect a gauge to avoid fuel spray.