If the MAF sensor stops working altogether, or falls outside of established calibration limits, (at least in US emissions certified vehicles), you will get a "check engine" light on your instrument panel. A code describing the sensor's problem will be stored in the engine emissions module, which can be read by a code reader. You can usually have the code read for free at any good chain auto parts store.
Since, as I understand it, you (a) live in Canada, and (b) drive a diesel VW, your emission control system may be different from ours.........particularly if your vehicle has been modified for biodiesel (not thusly equipped from the manufacturer).
I'd be more inclined to suspect another type of fuel issue if you are not seeing a "check engine" light (such as a clogged fuel filter). That said, to answer your specific question, if the sensor is bad, replace it.....they aren't that expensive.
doc