I keep mentioning that because just being lean won't cause that popping, maybe if it was super rich. The only two times I encountered that was due to way incorrect ignition timing from a distributor installed a tooth off (but it wouldn't idle without throttle), or one of the cams slipping. I personally would check things in this order:
1. mechanical (cam) timing
2. exhaust leaks, which will wreck havok with wideband reading
3. unplug both primary O2 sensors and reset ECU to lock trims at 0, then tune your fuel injector base setting until it idles and reads about 14:1. In fact, best way to tune is to do all your tuning before you let the ECU take over.
I only brought up ignition timing because 30+ degrees at idle didn't seem right to me, been a long time since I looked at a log but I was thinking my car idled at 20-25 if that.
Also, fresh fuel. E85 goes bad SUPER quick, like you might as well throw it away after a couple weeks quick.
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