No code reader. Checked gauges, air fuel gauge is irregular

 

Should have stopped by an O'Reilly or AutoZone and they could have read it for you. All anyone can do here is make a guess what could be causing it, and it could be any of a large number of reasons.

 

What do you mean by irregular? A supposedly common issue on Ecoboosts is the low fuel pressure sensor (LFPS) goes bad. On the air fuel ratio gauge, an indication of a bad sensor would be the engine going very lean (instead of very rich) on wide open throttle application. I presume there is a similar sensor on the 5.0.