There is a loud "rushing air" sound upon acceleration on my Sequoia

What is your question?

No engine light or code - doesn't seem to effect performance - (i bought it used, and don't know if it's "normal") There is a K&N high flow filter installed. Sound doesn't happen when cold - once engine heats up, when accelerating from stop, the noise is really loud (like you're revving the engine in neutral) - more FAN noise than loud engine - like air is escaping from somewhere. automatic transmission - sound only happens in low gears, from stop - once running 20-30mph, sound goes away