I just installed a Pac-Brake with the heavy duty exhaust springs and the plug in the flapper. It activates and deactivates properly. It appears to make the full travel of 90 degrees from closed to open. I have only driven it approx 5 miles in town and am wondering how much retarding effect this unit should have? When at idle as soon as I apply it I can definitely hear it. Maybe I was expecting too much but it does not seem to have much retarding effect. Will it improve when I hook onto my 5er and go on the highway? Thanks, John.