Where is the Fuel Pressure Regulator

My car is hard starting. For a few years, the engine would lack power in the morning when cold, but after a block of driving would operate normally. Recently, it has gotten worse.

When starting, it may take multiple tries to get it going. The engine starts, but immediately lugs out, like it is not getting enough gas.

Once it is going, it often runs fine for about a mile, then dies when the rpm's get low at lights or stop signs.

We have replaced the purge control valve (which fixed the only trouble code), throttle control sensor, and fuel filter. We have also put through some cleaner to clean the MAP sensor and injectors.

Our next best guess is the Fuel Pressure Regulator. We cannot find the part, though. The model year is close to a year where there was a change in design, so maybe we are looking in the wrong place, or maybe it is not there at all.

We would also like to know how the check the rail pressure if there's an easy way to do it?

We are open to any other suggestions for things to try. Thanks for your time!