bad afr

I bought a 2019 Mustang GT from a dealer. Car was originally from Alabama. Came with Headers, Intake, and a Tune. I’ve been putting 93 in it for about a year now and just seen a post abt somebody’s AFR reading 9.8 at cruising and Idle, and 20 at Deceleration. People wear saying it’s on an E85...

Hi guys i have a problem with my AFR at idle , the data usually fluctuates between 14.7 and 20 is usually corrected but fails again randomly , as a mod i have an edelbrock supercharger 2300 Tvs