Was it doing that before the tune up? It almost sounds like the change mine went through when I upgraded the intake. Is the airbox sealed good? Check the whole intake, from the fender to the engine. Mine is also loudest at about that rpm (not real sure, no tach). You might just want to replace the whole intake system anyway with some sort of cold air setup. That way you'll know where the sound increase came from, where the extra hp came from, and you probably won't be able to hear the noise anyway.
Good luck
Btw, my car drones too, but generally only when my wife is riding in it.
