00 2.4L Bogs down badly

Hi there:

I've been battling with this 00 Tacoma 2.4l for over a year now and I can't seem to find the cure.

The truck drives normally about 90% of the time, but every now and then will bog down almost to the point of dying. I will have to accelerate really hard to keep it from stalling. Sometimes I turn it off and then on and it will work ok for a while.

Things I have done in the past year;

complete engine rebuilt
new spark plugs
new coils
cleaned injectors
replaced coolant temperature sensor
new fuel and air filter
new oxygen sensors, front and rear
fuel pressure read normal
performed induction cleaning of fuel system

I swapped the Air Mass Flow sensor with another one from my friend's truck and it made no difference, unless his sensor was bad too. When I unplugged the sensor, the truck dies.

Occassionally I will get a check engine light which is related to the air sensor (O2S), but I replaced both recently with OEM Densos, I also checked their performance with the OBD scanner and they seem to operate within specs.

At this point, I'm running out of ideas on what else to inspect. If you guys have any pointers or ideas, I will appreciate them very much. At this point, I can't go back, I have to have this truck up and running as it's going to be used for work.

Thanks in advance.