We recommend that everyone read this and think about how 1-2 points in A/F ratio can ruin your engine or melt your $1000 cats.
There are serious concerns about how the accuracy and how these low cost - non OEM grade meters are effected by temperature, long and short term aging, when to replace a sensor, how to calculate them, response time (if A/F lines up "with engine rpm) and the effect of various fuels and additive and moisture are also an issue.
Kenne Bell kits are all factory calibrated with OEM quality A/F meters. Unfortunately, many of our customers compare our accurate A/F ratio to a dyno "cheapie" sensor/meter and then "re-tune" to the WRONG A/F ratio. That's our most time consuming tech problem at Kenne Bell.

Link to shootout : Wideband O2 Sensor Shootout! | FordMuscle Magazine

Link to Kenne Bell Dyno Testing Variables and Air Fuel :