Originally Posted by Arthur Dalton

These HFM -MAFs are more inclined to loose there accuracy/sensitivity from contaniments due to the fact that they are a Film Mass type sensors. The older/earlier LH MAFs had a Hot Wire circuit that would burn off any contaniments each time the car was turned off by a heater cleaning circuit .
So, even a thin film of smog will effect the HFM ones...air cleaner maint is a must , as is periodic cleaning of the A/F box . Performace , oil bath filters are also known enemies b/c they cause a thin oil film on the sensor..
As far as those codes are concerned , MAF is the most likely culprit, but before jumping to that comclusion, be aware that both Fuel Pressure regulator and vac leaks will cause the same , along with any unmetered air leaks. These should be check first , specially the Fuel Pressure.
The injector duration mapping on these is specific from design to operate at pre-determined pressures..and they have to be in that spec zone to work correctly. If the ECU has to adapt beyond normal limits [ rich or lean] to adapt the fuel trims for an over rich or lean condition, it will bring on those codes. Air leaks cause a lean condition and high fuel pressure will cause a rich condition..the system will correct for either only to a certain point, upon which a code will be triggered ...so, is the code telling you that the MAF is bad or is it telling you that that correction limits have been reached..........
It is not uncommon to have a fuel regulator vac hose or diapragm leak ..this allows either too high a FP or , in the case of a leaking reg diapragm, unmetered fuel getting sucked into the intake... a simple FP test and a quick look at the reg vac hose will tell the tale..and you can change the MAF until the cows come home w/o solving the problem if that is the case.