Save yourself some trouble and DO NOT install that gauge.
There is no way a rinky dink A/F gauge can properly get an accurate reading or your true O2 reading.
If you had a wideband 02 unit, yes. But I'm guessing this is just an autometer or some sort?
Go with a fuel pressure gauge and an EGT if anything. Fuel pressure should increase 2 psi with every pound of boost, and if you watch the EGT or have playback, it will dramatically rise over normal conditions if you're running lean. detonation = rampid EGT's = time to let off the throttle.
I had an A/F unit with my J&S safeguard matched with a V-Afc in my old Civic Si. It was worth nothing...poop. The kid who bought my car, played around with the fuel pressure, and went with different injectors...viola. He solved the problem; the car was running stoich on the LEAN side and the J&S unit was pulling back my timing. I never figured it out.
There's no way an A/F gauge will work just by tapping in to one wire. The computer's not smart enough to send all that information through one or two wires. The safest bet is an EGT and a FP gauge.