Rich and lean at the same time... this is an interesting problem.
From what I read this is usually an oscillation problem. Bad O2 sensor, but you already checked that.
Check the MAF.
When you got the "misfire" at restart, were there any loud bangs that might have blown open a vacuum leak somewhere? I think this is less likely.
Also, some ideas here:
https://ls1tech.com/forums/lt1-lt4-m...-bank-2-a.html