Don't believe the people who tell you aftermarket filters release loads of power, they don't. On my old Golf GTi the difference was 3 bhp (the operator could make that difference) and having tested foam (Ramair- identical to Pipercross) against K & N on my Caterham there was no difference at all.

Especially not drop-in filters that fit in the standard airbox. The factory filter itself very rarely presents any significant restriction when compared with the airbox shape / volume, intake snorkel width, etc

a small anecdote for you, don't groan at the back there..:-)

my first car transporter was an ex Toleman 9 (nope, 10 car) car carrier Iveco, dreadful thing it was running really badly and hadn't been looked at for about 6 months that i know of (yes operators were that bad at times), i asked the company er fitter when it would be serviced next, he looked aghast at me squarely in the eye ''we don't service them'', he wasn't joking either.

so i removed the air filter or rather pulled a drum shaped block of filth out of the filter housing and binned it and ran it without a filter and it pulled much better for that, it died about 6 months later, still unserviced, good riddance.

Thinking about it, i've never bought a sports or washable filter that i can recall, as lads we nearly always ran our Weber carbed cars without filters (enjoy that intake roar) thouh have been known to stretch a stocking over the carb to keep the largest of the nasties out.

Edited by gordonbennet on 29/10/2015 at 23:17