The acoustic valve is behind the passenger wheel arch.
Taken from another thread.
* Remove (entirely) the air box, disconnecting both air feeds (one to the right and one directly under).
Air box is held in place by two screws and jublie clips
* Jack the car up under front left, ensure you use a axle stand or similar
* Remove wheel, place neatly elsewhere
* Remove the underside arch-liner, fastened by a few torque screws and some fat looking plastic plugs
(these just pull out with a tug)
* Watch for the small ribbed cable (battery acid overflow pipe) as its connected to the arch liner. Let this dangle somewhere.
* You will now have exposed the underside of your front bumper, note the bracket holding both your horn and the acousticvalve.
* Try to unclip as many of the wiring looms to both the horn and the valve, let these looms dangle somewhere
* Undo the bolt holding the bracket in place
* Tuck the horn assembly somewhere out of the way
* Remove the small air feed, no 1, simply turn it to unclip
* Remove accoustic valve by pulling it downwards and out of the wheel arch, if you meet resistance check looms are disconnected and path is clear
* You should be left with a large gap / hole
* Accoustic valve will be connected to a thin black tube, remove as much of the connecting bits, leaving just the tube.
This must be blocked off (or you will idle above 1000rpm) with a screw / bung similar
Tape the screw in place
* Remount the horn, reconnect horn wiring loom to horn, screw bracket back into place
* Tape up all looms and cover ends with tape
* Tape blocked pipe somewhere
* Once the valve is removed make any modifications you wish, i.e place your airfeeds etc
* Reconnect the battery overflow pipe to the grilled bottom of the arch liner
* Replace arch liner, fix with plugs and screws
* Put wheel back on, ensure wheel is flush to brake when placing nuts or you will mark your wheels
* Lower car
* Connect new air feeds to air box, replace air box, ensure jubile clips are tight
* Job done, admire your work.
