How to untrick the pneumatic muffler valves?

[Jettafanatic]

In a nutshell: when i bought the car , I had noticed the car was not as "quiet" as everyone complained about.
When I removed the original factory exhausts to put Tubis in ( I do my own wrenching...), I noticed that to begin with, before I did anything, the valves where always open... even at idle. And in the engine compartment I see a disconnected cable with a resistor bridged in ( like you do when you bypass a sensor)... Anyone know how to "untrick" ( which I am sure was done) the pneumatic valve control so I can put the original mufflers back in with the flappy valves working and thus keep my wife happy? Car's pretty loud right now..... And no, they were not wired / zip-tied / glued open...

Thanks!!!