I recently purchased a K&N FIPK kit, installed it myself and checked for leaks. Everything was fine for a month but then I began hearing a whistling sound coming from the engine area at very low RPM's. Does anyone know what is causing this? It seems like the low end is very sluggish and lacking the power it first had.

Keep it real

 

sounds like the typical k&n sound to me. not sure on the low end. it is getting more air now. could just be a different feel to it.