I have just installed an O2 sensor (2 wire) in each of the exhaust pipes back near the fuel cell with a gauge for each, a dual EGT gauge with TCs in the #2 and #5 header pipes, and an electronic fuel pressure gauge (no gas in the cockpit and getting those isolators to burp is a royal PITA). So I can see EGTs, fuel pressure and O2 readings at a glance, in addition to the engine oil temp & pressure, water temp, voltage, RPM and tranny oil temp. This is overkill on a street or even AX car but is cheap insurance for a track only car. Perhaps the best of all these is the fuel pressure gauge. Weld bungs into all 6 header pipes, tune and then run. Put sensor in and out of the 6 on different runs and see if there is any difference.