I am wanting to run a mechanical boost guage to the center speaker, but I can't even figure out how to get through the firewall? Where can I get out of the firewall into the interior? Also What wire can I use so that the boost guage LED comes on with the headlights?

 

Search for 'boost gauge install'. There are many, many threads.

As for routing through the firewall:

 

Is that the passenger side fender well?

 

Driver side in an LHD car.

 

Thanks, I found it but what all plastic do I have to remove to get it to the center speaker?

 

Remove the grille, carefully.
As for a power source for the light, most use the wire going to the ash-tray light. Easy to access and it will even dim with the rest of the dash.

 

some self promotion:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/din-panel-gauges-577232/

 

i removed the speaker grill and fished a coat hanger down to the drivers side...really wasn't all that hard....good luck..

brad

 

You can also poke a hole through the big rubber gasket for the steering wheel shaft, thats what I did, (so did alot of others) and it works great, search around, I'm sure theres athread on it somewhere.....and splicing a longer lenght of wire to the ashtray light is not only easy, but gives the light in your gauge the same 'fade ability as the rest of the lights in your dashboard, so ya, thats the way to go...

 

Poking a hole in your steering shaft boot, sounds like a bad idea. I've had to replace a shaft on a car because the boot had a tear in it and dirt got in there over time and just trashed it. Not something you would want to go out at 120mph.