on some 2015 and 2016 WRX/STI and Forester XT Inspect and replace turbocharger air intake ducts stamped April 2015, that may have been produced with an incorrect material that is susceptible to cracking. Should the turbocharger air intake duct crack, the engine may develop a rough idle, ...
Fast road camshafts normally increase the performance through the rpm band, you may lose a little low downtorquebut your higher rpm power will be higher. Race camshafts, increase the higher rpm power band but as a result the car will not idle smoothly and low end power nearly always suffer...