Hard to start

What are some possible causes? I've replaced the fuel pump assembly once with a new(er) assembly with fewer miles, yet the problem persists. Since the problem still exists after the pump swap, i'm less inclined to believe the pump is the culprit.

You need to verify the fuel pressure if its within specs-could be leaking down somewhere such as the injectors and fuel pressure regulator and fuel pump check valve-that's causing the hard starts

Is there a way to check the fuel pressure regulator? I mean, i know how to test fuel pressure, and i know it should only drop 5-7psi upon shut-off, but is there a way to actually test each potential problem individually?
Like i said, i replaced the pump assembly once already with a newer model, so i'll be testing the regulator first, if there is a simple way to do it.
As far as injectors are concerned, could they be leaking fuel into the cylinders, and back into the tank? I'm confused on that one.

what do your plugs look like? did you check for engine codes?

Checked the codes, It just refers to a (known) catalytic efficiency problem. Nothing else mentioned. Could be related, i know, but i doubt it.
Haven't pulled the plugs out yet, waiting for a clear day.

any progress?