140 Firewall Access Points
 

Just installed a manual boost pressure control valve on my S-350 and I want to install a boost guage in the ashtray where I can check boost pressure when I want to. I have just about ruled out trying to route a hose through the firewall, but I have found a boost pressure guage that has a transducer and transmits its data over a regular wire. I know there is bound to be a wire going through the firewall that is not used by anything in my car. Problem is finding one. Can anybody help me in this area. I know the S-500 and S-600 have more features and possible wires, so my S-350 possible would have one unused.
Thanks!

Why have you ruled out running a line through? There should be plenty of points where you can run a line through an existing grommet.

Matt.