I notice people use aftermarket filters from time to time. Genuine filters for the D2 really aren't that expensive if you can get a bit of discount from TPS. Service stuff like this comes under their 'Parts Club' promotion with usually close to 50% discount, the same as with oil.
The cabin filters now come as a pair on part number 4D0 898 438A. Retail price is £52.85, Parts Club only £29 (inc vat). The genuine ones are proper activated carbon, and actually fit properly. Fitment on some of the aftermarket ones is horrid.
Air filter 077 129 620D - retail £24.40, Parts Club £13.40.
FL V8 oil filter 021 115 562A - retail £18.34, Part Club £9.53.
