You won't have to bang on the firewall. You will have to move the igniter to a different location, and bend the bracket for the cruise control thing to move it outboard, both easy fixes. I bent the AC line down a little to give more room. If you want a TMIC, get this one. He is not that far away from you either.
also requires either taking a section out of the clutch master tank to lower it (if you have a manual), or find one of the offset tanks. another option, which I am getting setup to do is a complete remote tank with hose and addapter. that way I can move the tank over to a area where I can get to it and eliminates the interference with the intercooler.
I have a Diamond ignition module that has a supper low profile mount that gets it low enough to clear the underside of the TMIC.
You will also have to move the coolant fill tank.
search the forum, there is all sorts of information on how to do this mod to a SS with current model TMICs
94 Silver Turbo Wagon 5MT/Walbro255/SS header/STi Gn Mounts/01 RS wheels