The genuine "factory-installed" LPG switch goes to the left of the T-bar (where the traction button goes on Acclaim and Calais). On this version the green LPG light will illuminate on the dash when in LPG mode.
The genuine "installed after manufacture" (but before car is sold at dealership) LPG switch goes under the trip computer switches. The cutout in the surround is exactly the same size/shape as the fog lamp switch cutout, and the bezel is the same just in reverse (i.e. sloped towards driver's side of the car, whereas the fog lamp switch is sloped in towards the centre of the car). AFAIK on this version the LPG dash light does not illuminate (unless it's been modded) but i might be wrong there.
To fit the switch under the trip computer switches: If you have (or have access to) a VT/VX SS or Calais just remove the fog lamp switch, put some thin paper over the hole and trace the outline with a pencil, then cut out the hole under the trip computer switches. A soldering iron tip is an easy (but slow) way to cut the hole, then carefully file with a fine metal file. Be careful though as one slip or mistake and the surround is stuffed/scratched. After the soldering iron has cooled down clean the soldering iron tip with very fine sandpaper to get the burnt plastic off.
(btw i don't have any pics as i had cut the hole & fitted the switch before the LPG install, only to be told by the installer i couldn't use it as my VT V6 s/c LPG system needed an aftermarket switch/gauge combination [i couldn't have both LPG and petrol on the factory gauge as because it's a V6 s/c the PCM pins needed for this to work were already used by the supercharger - if it was only an ecotech it could have been done apparently]. So i sold both the LPG switch and dash surround in late 2007)
No, I dont believe the ^ is correct.
The lpg switch only goes in the gear console on the automatic if there was no traction control fitted. If traction control fitted the switch goes under the mode buttons.
Im not sure about the manual, if fitted traction control goes on right of steering column under the headlight switch,which would leave the lpg switch to go under the mode buttons, but if trac not fitted perhaps the lpg switch goes on the right of column
Yes, factory system disables traction control when on lpg, that doesnt make the switch superfluous. Traction control can still be used when on petrol and the switch used to activate/deactivate it according to need.
AFAIk, no lpg kits were installed at the factory, only factory approved/designed kits that were fitted after manufacture by licenced gas fitters; either organised by dealer before purchase or by owner after purchase.
