Hard starting intrigue

So I've had this problem for a while, tried a few fixes to no avail. My wife's car is a 2000 Intrigue GLS, and for quite a while now it has been a hard start. You turn the key, starter cranks up and you have to give the engine several good cranks before it sounds like it picks up. Even then quite often it will simply die as soon as you let go of the key, or else drop down to about 200 RPMs and then rev back up. After this you can start again no problem, or sometimes it will seem to idle a little rough until you start driving. I have replaced spark plugs, cam/crank sensors, fuel filter, cleaned the throttle body and the O2 sensor, none providing any solution. It typically will start better if it has only been off for a very short period, but if longer than a few minutes will still be hard to start. Does anyone else have this issue?

Jpar -
Have you checked the FPR (fuel pressure regulator)? Many, including me, have fixed starting problems this way.
Search the forum for "FPR" or "fuel pressure regulator" to see other cases of this, and how to diagnose.

I'm fairly certain I checked that, but I don't know if I checked it correctly. Wouldn't hurt to check again, so I will as soon as I am able.