95 zetec acceleration problem

Helping daughter with 1995 Contour 2.0 L Zetec ATX.

I have read a ton of threads but can't seem to find anything that's the same as the problems with this car.

The car doesn't want to accelerate at low throttle, feels like it's not getting enough fuel, but the fuel pressure is good and when you stand on the gas it accelerates well.
Doesn't seem like it's a fuel pump problem since at full throttle the car accelerates fast.
The idle is low and smooth.

We have a code 172, system lean and have checked for an air or vacuum leak but there does not seem to be one.
Emmisions: High NOX, very low HC & CO

Car is new to us and we have already fixed the problems it came with.

New front springs/struts, thermostat & inlet housing, DPFE sensor, EGR cleaned & tested, MAF cleaned, new cat & O2 sensor, new TPS sensor.

I am running out things to check and any suggestions are appreciated.

Problem solved.
For others having symptoms like this.

The MAF sensor was underreporting the amount of air coming into the engine.
It was difficult to detect the problem because the MAF was working and correctly reporting air flow at idle, but at higher air flow it was a bit off.
Replacing MAF allowed the PCU to deliver the proper amount of fuel to the engine.