I wanted an easy way to be able to left-foot brake in SCCA rallycross events without sending myself through the windshield, but without permanently modifying or replacing the OEM brake booster. I also wanted something that would enable me to quickly hook the brake booster back up for daily driving. Here is what I came up with for under ten bucks.
All you will need is:
3/8" brass hose barb to male pipe fitting
Brass cap for said hose barb to male pipe fitting
Small hose clamp 1/4"-7/8" (I used MasterPro hose clamps with removable key from Oreilly Auto [Part # MP6R004V] for a tool-less installation once I arrive at the event)
Locate your brake booster vacuum line (The only rubber hose coming off your brake booster, typically located under or to the left of your master cylinder)
Loosen the clamp and pull the hose from the booster (It will "PSHHHHH" don't worry, this is normal, you are just releasing the vacuum from the booster)
My clamp was a pinch-type clamp. If yours is the same, take that crap off and chuck it in the bin.
Replace with the shiny new hose clamp you got from your auto parts store! YAY!
Now, I lock-tited the brass cap onto the pipe fitting to make sure it wouldn't leak. Any thread sealer will do nicely, but isn't entirely necessary. Really this is just me being extra careful.
Now, say you've just arrived at your rallycross (or autox!) and you want to activate your LEFT-FOOT-BRAKE-ACTION!
Just remove the brake booster line (and enjoy the PSHHH),
Cram the barbed brass pipe fitting into the end of the rubber vacuum hose, and secure the hose clamp around it.
At this point, I zip tie the hose to something to make sure it isn't flopping around while I'm driving. I encourage you to do the same.
After you finish your rallycross (or autox!), just clip the zip tie, loosen the hose clamp, remove the barbed pipe fitting, reinstall the vacuum hose onto the brake booster, tighten the hose clamp around it, and you're good to go! I keep my barbed pipe fitting in my glove compartment so I never forget it!
You probably shouldn't drive around all the time with your brake booster disabled, but ultimately that's your call, and your consequences to deal with should something happen.