In the turbo world it seems everyone installs a "high flow" air filter. But there is serious doubt if they improve performance. Add a new air box, cold air intake, new hoses etc and the vehicle will sound different but real measurable gains on a Dyno are elusive. Only after upgrading the tune or turbo do you see real performance improvements.
Install the K&N if it filters better and you want it, but don't expect more horsepower.