Where is the fuel regulator located on ford explorer 1999?

On a 1999 Ford Explorer, the fuel pressure regulator is integrated into the fuel rail. It's not a separate component like on some older vehicles. You'll find it on the fuel rail itself, usually near the intake manifold. To be precise, you'll need to look at the top of the engine, near the back, following the fuel lines. A diagram or a repair manual specific to your 1999 Explorer's engine (4.0L or 5.0L V8) will provide the best visual reference.