Question on A/F guage reading?

[hvfun]

I had my rear mount mcx apex in shop doing alot of things. Fixed air leaks, new valves, Swain coated exhaust, RX1 header pipes welded to mcx pipe. I road it breifly on trail and seemed to be way rich on low end. Just got A/F innovate working and it says from 4.5 to 5 at low speed. Haven't ridden yet. What could have changed the A/F from 12.5 down to 4.5. Yamaha CO set at 0 both times, tried leaning out to -20 and still read around 5 when ideling.
Can anyone help me with this?

 

[hvfun]

any ideas anyone? Could the innovate box be calibrating wrong? I went through the steps to calibrate it and put in a new sensor.

 

[BigFish BC]

make sure you have a realy good ground that will cause erratic readings.