Completely normal. its the crappy OEM Tune, there are actually 2 power dips but that one is most noticeable. after about 5500 or so it falls on its face againI have a 2017 WRX manual trans. when accelerating between 4k and 5k rpm it backs off or has some hesitation. once I reach 5k rpm it picks up. The dealer service manager drove it and said this is normal. anyone else experience this?