It is an autometer with the LED's. I am not sure if I shoudl hook it up to the ECU or the stock O2 sensor. I asked the local speed shop if I should get a wideband O2 and they said they would use one to tune it, but it was not necessary to install it into the car. I also have the Apex-i SAFC, but it is not mounted where I can see it when I am driving so I just wanted something on the A pillar to reference when I am driving.
Really the narrowband sensors are just about as worthless as could be. They can accurately depict AFR (Air Fuel Ratios) from 14.5 to 14.8. If your meter is reading 12.xx, then the actual # could be anywhere from 14.5 to less than 10:1 AFR, and there's no way to tell. once you move more than 1 or two tenths from stioch, your pretty much screwed... and there is no repeatability as far as AFR's beyond the 14.7 stoich range either, say if you compared your output to a wideband and then use that as a reference, it won't stay the same each time, so really its very hard (to impossible) to tune with.
If you've got something as nice as a Mk4 TT, Invest in a wideband sensor.
The two I'd been looking at heavily are the Zeitronix ZT-2, and the Innovative Motorsports LM-1.
They both offer some very nice computer logging features, but the feature that reallllly grabs my attention is the mountable LCD readout for the ZT-2. It's the kit I've been thinking about getting myself.
Also, with the base prices being $349 for the LM-1 and $279 for the Zeitronix (Not incl. LCD Display, $399 with it) makes things even more tempting. However, in many applications to get the most outta the hardware it's nice to have a laptop to do wideband logging on. So, instead of nitrous runs where merely watching a gauge rise or fall you can log it.
Personally, the ZT-2 is the way I think I'm going. $399 for the whole package, it can take inputs from other model EGT sensors (which I've got), simulates a stock narrowband signal for the stock ECU, does 9 hours of datalogging, has inputs for boost and TPS and so forth, etc...