I would like to replace the 2 long breather hoses that go back to the air filter on my S3 with a couple of K&N or PiperX crank case breathers.. I don't have the car here at the moment so can't measure but what size do I need..?
The one from n/s rocker cover to the air filter is 13mm and I guess the other one you're after is from o/s rocker cover to inlet plenum ? that ones 10mm