Beware. The genuine BOSCH part MAF you find at third party sellers haven't passed the tests that Porsche have in place for screening out bad sensors.
BOSCH sells them to private sellers for cheap, instead of putting them in the garbage. It's not that they don't work, they are just not meeting specs for a Porsche Car. Often called aftermarket MAFs e.g. eBay MAF sensor or those you find at 200~300 here and there.
The reason the P dealership's is $500+ is because it is a 'sensor' that actually been scrutinised and works as it should
Go ask them!