The ARM Motorsports 2.0T air filter is the best option to increase horsepower on your 2.0T without getting a full intake system.
Improve airflow and add meth ports with an upgraded 2.0T Throttle Body Pipe
Increase power up to +10whp with an 2.0T Turbo Outlet Pipe
Increase power up to +15whp by upgrading the intercooler inlet and outlet piping
Catless Downpipe boosts your A3 2.0T +20whp and +30wtq
Full 2.0T Intake System increases airflow, power and sound!