I thought I understood how the resonance flap operates, but some things aren't making sense. Looking at this link: http://mmm-five.net/Articles/files/E34M5_IntakeResOverhaul.pdf it explains that it increases torque at less than 4000rpm. The torque curve also confirms this. What doesn't make sense is that when the flap isn't working, due to failed actuator or deteriorated vacuum lines, a loss of torque is noticed. However the actuator is in the extended position (not actuated) below 4000rpm, so I would think you wouldn't notice any difference below 4000rpm if the system wasn't working. I would expect a lack of HP in above 4000rpm with a failed actuator system. What am I missing?