2-1-2 is faulty 0-2 sensor or signal missing.

The wire to the ECU could be faulty so I would check it back to the ECU with a ohm meter. Unless you have ruled that out.

The symptom is lean mixture for the computer. Excessive air or lack of fuel.

If you have ruled out vacuum leaks around the engine and from the cabin vacuum motors. Port open and hose good to the FPR.

I would replace the fuel pressure regulator with a known good one.

It adds fuel under load demand and that would cause the symptom of flatness of power. The ECU responds by retarding spark to prevent premature detonation (knock). This engine probably has a knock sensor and it adjust so fast you are not aware of it. Unless its called "lumpy".

Is it a little cold-natured when driving off while warming up?

Your mileage is just a tiny bit to good but the feeling under you foot, isn't.

Best guess from here,

Phil