I am driving an 89 GXL converted to Turbo with JDM engine. Just rebuilt and streetported with Pineapple porting template. Ported wastegate and running stock turbo. I have a FMIC and a Supra Twin Turbo fuel pump. Monitoring with LC1 for AFR.

Onto the problem...
I have had three times recently under boost, hard on throttle, where I backfired and had what felt like a miss All three times very quick, backfire with hesitation and then immediately back to normal. While cruising home today, AFR was about 14.7 and cruising nicely. I had a quick stutter where the AFR went down to about 11.3 and then right back to high 14s. This was very quick (about as quick as snapping a finger). Not sure what would cause this but it is pretty disconcerting. Any ideas.

 

Ideas:
Dropout in the air flow meter (AFM)
Intermittent grounded circuit to AFM, one or more injectors, or ?
Intermittent open in the O2 sensor circuit (ECU would interpret as a lean condition, and richen the mixture to 'correct')

 

I have wondered about using the LC1 analog output to wire in place of the stock wideband. Any advantage or disadvantage to doing this?