Subject: 1998 Eclipse GS fuel system
Question: Where is the fuel pressure regulator on the eclipse 420a engine or do you have schematics for the system its self?
Answer: Greg,
The fuel pressure regulator is located on/near the fuel rail. Look for the hose that goes from the fuel filter (on the firewall of the passenger side) to the fuel rail. The rail is between the head and the intake manifold.

Good luck!