AEM gauge AFR reading vs. VCM scanner

30-4110. Correct formula in VCM scanner is being used. I log in lambda or gas AFR and no difference in issue. Gauge is reading about .5 AFR richer at idle and .6-.7 richer in PE compared to the reading in MPVI2 Pro VCM scanner input. Same difference when logging in Lambda.

I'm familiar with if there's a ground voltage offset issue and I've grounded the MPVI2 pro input directly to the same ground the gauge is using and there's no difference compared to the default grounding of that through the OBD port.

I know I can modify the formula to get the Scanner to reflect the gauge's values. Which one do I trust and go with? I hesitate because I'll be adjusting the AFR's when logging to be richer than currently reading, so in theory I'll be leaning out my PE when adjusting my MAF on next tune cycle.

Thoughts? Any experience on this gauge that is similar? I wish I had another wideband to compare to. All I have is the factory narrowband on the same bank as the wideband and it bounces high/low around stoich as it should, whereas the wideband usually stays on the richer side of stoich between 14.3-14.8 when in closed loop. (scanner shows 14.6-15.3)

This was resolved by grounding the AEM's ground to the grounding output from the MPVI2 pro ground output wire. That uses the 'signal ground' from the obd2 port vs. chassis ground and there was a slight voltage difference between them. It didn't affect the gauge display but it did align the output signal from the AEM.