Hi, the way I read your gas readings(before the re-set and directly after) you can not afford to ignore fuel pressure and flow checks.
If both are within spec, then the injectors need to be flow checked(glase build up)

In the following section I have simplified the ECU fueling process(its not perfect but near enough)

The ECU receives the mass air reading(sensor output voltage) and depending on load and engine temp, it uses a look up table(software loaded in the ECU)to fire the injector for a set time to attain an AFR (Air Fuel Ratio) of 14.7/1

The amount of fuel that will be injected for a set injector duration will depend on the pressure sitting behind the injector, the ECU can not measure the pressure in this system so it has to take it as read.

If the pressure was to high then more fuel would be injected for the same duration and vise-visa a lower fuel pressure would result in less fuel being injected

When the ECU reads the information from the AMM it applies a injector duration to suit the air mass entering the engine (lets call this the "mean" fueling).

Now, there is always a band(fuel trim) either side of this "mean" duration which is used for fine tuning the fueling(subject to the feedback from the O2 sensor).

If the fueling of the engine stays within the scope of the "look up tables" then the ECU is happy and the MIL stays off.

Only when the sums do not add up(as far as the ECU is concerned)does the MIL light up and a fault code logged.This happens when the limits of the adaptations(band width)are reached and the AFR is still not right.

If a fault code is logged saying upper limit reached, then the ECU is reading a weak mixture and is trying to richen it.

If a fault code is logged for lower limit reached then the opposite is true and the ECU is reducing the fueling to try to weaken the mixture.

Now you have to think of all the things that may cause the system to read either a rich or weak mixture.

As an example:
If the AMM is registering less air than the engine is using then the ECU will start off reading the output voltage of the AMM and doing its maths, then it will receive feedback from the O2 sensor saying that the mixture is weak, it will respond to this by adjusting the "fuel trim" in the positive way (more fuel).

It(the ECU) would carry on doing this until the feedback from the O2 sensor was good or until it reached its limits(MIL on).

Example no two:
If you had a small hole in the exhaust pipe up stream of the O2 sensor then this is likely to draw in air, which could cause the O2 senor to read a weak mixture(this would be false), the ECU would respond to this by increasing the fueling until the O2 sensor reported back that everything was good or until it(the ECU) again reached its limits.(in this case the true mixture would be very rich)

These are just two of many things that can and do effect fuel trims.
If we now think about what effect low fuel pressure could have on this system, we will see that guessing and assuming things will not cut the mustard. HTH

Regards Mark.