Yes have used K&N filter before. in a ford and a petrol peugeot.it did
make alot of diff and had a little bit more power from the ford,they are
not cheap.the peugeot had power before we fitted one.it made a little
diff to it,you could hear the air being sucked into the carb when you
hit the pedal.
so have fun from Chris Addlestone Surrey..

Be careful with induction kits.  I think you will need a cold air feed one
as the ones that take the air from the engine bay, suffer in the summer as a
friend found out on his GTi.  He had more power with the original box!!

I had a K&N on my GTi and have a Jetex on my GTi 180 and made them both pick
up quicker.

Same as my Xantia. Have fitted Eastcoast Racing 27bhp power upgrade box.
They require a K&N air filter to be fitted when boosting to that additional
amount. About £35- drops in the airbox as a straight replacement. Give it a
clean at 18,000 miles and it lasts forever.
DaveK.

i've put one in my Hdi there is lillte difference in perfomance
compared to the standard filter when new. its when the filter gets
older that the performance of a K&N is better. AND if you plan to chip
tune your car a performance filter is the obligatory accompanion to
that.
and induction kit is nonsens on a Hdi ( try and find one with the
right diametre)

apart from that, for the price of four filters you get the K&N which
saves mony from the very first Km after 60.000Km..

make sure to clean your filter each 15.000Km or so  ( depending on
road conditions)

happy motering

Marc