The fuel pressure regulator is buried under the upper air intake and attached to the rear end of the passenger side fuel rail. I would exhaust all other easy diagnostics before moving on to the FPR.

To check the fuel pressure without changing anything on the OE setup requires a special fitting, but there is a shadetree way to check it without the special fitting. Cut the fuel line near the firewall and insert a tee fitting. Install a pressure gauge and check pressure. When you've finished, either remove the upper intake and replace the fuel line - or just leave the tee in the line and plug it.

Frank