im hearing a strange 'wah wah wah wah' noise whenever the engine is running around 2400 rpms, happens in neutral and all gears. it seems like its losing a little power while thats going on and whenever i get past 2700 or so it goes away and feels normal again. its loudest in the lower gears but i can still hear it in 5th. any clue what this could be? thanks

j-slick