I only tracked this down after playing with the software logging.

I noticed I was getting duty cycle / injector ms spikes.

After further investigation, it turned out that my tps was bouncing around slightly (going down to 99 and back to 106 in the worst case) and dumping a ton of fuel based on the accel enrich maps.

To fix this, I got rid of the accel enrich settings in mid-high boost and lowered voltage for TPS open.

The TPS tests fine and does a clean sweep when the car isn't moving. I'm thinking it may be vibrations/bumps in the road causing the funny readings.

anyway, this totally fixed my erratic AFRs and funny little stumbles. Just thought I'd give a heads up about this possible issue. Its probably wise to make sure accel enrich rate load is at 0 from 71 and up and to give your TPS a little extra headroom (ie: reads 106 a bit before youre actually flooring it)

 

I had this same issue while on a long road trip, the problem occured in canada

I had a loose ground in my harness