One of the "challenges" of MAF tuning is having the proper "tools" to get it right. As an example, some "high flow" air cleaner systems introduce vortexes in the intake tract that don't exist with a stock air cleaner. So, at any given throttle setting, how do you tell whether a MAF is reading laminar air flow, or a vortex induced by the air cleaner? The same situation may exist when an aggressive camshaft is installed. Reversion and other abnormal (compared to a stock system) intake flow characteristics may leave the mass air meter reading a vortex rather than laminar flow at various points. And these vortexes may change considerably depending on degree of throttle opening and engine load. So the question is, how do you determine what the MAF sensor is actually reading, and whether it's reading consistently at a particular flow rate? I'm not suggesting that it's impossible to make those determinations, only that most people won't spend the time, or don't have the tools to do it. As a result, many MAF tuners have become known as big wheels because they run in circles.