IMO its not 100% going to be down to the engine oil vapor, I cannot see how oil can get blown back on to the maf element? Look at a 1.8t DBW MAF and you will see what I mean. Plus when you lift off from under load the air is pulled towards the turbo , because the turbo is still spooling and pulling air in at a lowe volume. If the DV is fecked the turbo would stall and the air would come come back toward the MAF.
If the vapour was comming back in to the maf the maf would be wet with oil like the inside of a IC pipe? It is down to ware and tear, constant heating and cooling of the elements, vibration, water vapour, dust, air flow errosion.
Cheap cone filters kill MAFs at a quicker rate due to added, vibrations, extra heat and larger dust particals being allowed it. Plus Oiled filters do cause issues, look inside a MAF from a car running a oiled filter and it will look like it have a sticky texture and dust all over the internal surface.
Plus MAF are degined not to last forever if you know what I mean.
On a car with poor crank/cam case breathing the oil vaspour can reduce the the power by a very small amount, fitting a catch tank can over come this. My calibra turbo had to have a catch tank fitted to stop it smoking due to the poor oem breather set up,When I went around a right left hand bend my induction took a nice gulp of oil which caused a flat spot.. The OEM breather set up on the 1.8t aint too bad so you should not see a gain in performance by fitting a catch tank.
Nick
