You can put a MAF and AFM in series and make a simple lookup table, but it will only be valid for the one air temperature that it was done at. The MAF reports kg/hr of air flow, and the AFM reports m^3/hr. They are related by density, which is primarily affected by temperature changes in daily life. Altitude also factors in. My converter does the density conversion in real-time so that the MAF's kg/hr output becomes true m^3/hr output for the ECU, since that is what it is expecting to do correct fuel calculations.
Resonance is a bigger issue with MAFs because they are much more sensitive. The AFM has slow response, but that gives the advantage of dampening the intake pulses so that the output looks smoother, albeit delayed. The MAF can easily resolve individual intake pulses and its output looks sort of like a sine sweep of varying amplitude and offset. Being that the sensor has a non-linear transfer function, you do not get good results when applying analog filtering since analog filters are, at least in their normal operating range, approximately linear. In short, putting an analog filter on the MAF output will cause you to run very, very lean at WOT. The filtering must be done in software so that you can account for the non-linearity of the sensor.
The filtering algorithms are set, although selectable by the user (and you can turn it off). A 6 cylinder would likely need less filtering than a 4, and an 8 would need even less thanks to valve overlap. Users do not need to tune much of anything in most cases, unless they are going stand-alone and want to really customize the air flow voltages to make tuning easier. Otherwise, everyone else can treat it like the stock sensor is still in there.
