For that need, perhaps best to get a wideband sensors that installs up the exhaust pipe with a temporary clamp (several kits). You need to run a cable to it, so maybe go up into the trunk and under the seats. Unlike narrow-band O2, wideband sensors control their heat so can work anywhere downstream. However, drawbacks of the rear mount are that you can't use well for close-loop control due to the time lag, and if you have any exhaust leaks that suck in outside air, you could get a false reading.
