I think this car has the LH 1.0 system and not a CIS.

I would be suspicious of the throttle body being dirty and possibly a gummy IAC.
The good IAC should allow the engine to rev up past its normal idle area and then shut it right back down to idle quickly. This is upon every start up!

The IAC and the throttle switch need to be synchronized. It might be something with these two are sticking and causing the hesitation.

Cleaning and Adjusting can go along ways to resolving intermittent issues.

The TPS has to tell the ECU that you are coming off idle. In that instance, the IAC is dropped out and the throttle plate has to just open and air flow blending begins.

There is a narrow band of overlaps of these three components.
I call this the overlapping, a transition staging area.

The FPR has a small role in affecting mixtures but it's purpose is to work under accelerations, so do not kiss it off completely.

If it's not leaking the rest pressure off, in that in the morning it hits right away after sitting all night,
it is probably OK.
It would really have to be screwed up to stick open enough to drop fuel pressure, so intermittently back to the fuel tank, while under way.
Doesn't mean it isn't getting stiff or slow!

That's why I want to leave a fuel rail volume or a fuel pump problem.
You have ruled out a number one cause, for the most part, by having good ignition components.

Things are more gummy until warmth hits them!

I know, because I am getting them bones! (:-(

Phil