If you want to display A/F ratio, it's worth investigating whether you can program an A/F xgauge. I was able to get one working on my CAN protocol Scion, but not with my (older)ISO protocol Nissan.
Unfortunately, the A/F display isn't very helpful. The leanest ratio I've seen so far in limited testing is 14.6:1. It goes to 18.9 with the engine off. I think I'll try this wideband oxygen sensor.
theholycow 
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