Baseline timing is 5 degrees w/o ecu control, not with it. +/- 3 degrees I believe.
Thats part of your problem.
Most 1g's on dataloggers yeild 02 voltage of .88-.94 when tuned properly, but just tuning by that is asking for a hole in a piston.
Set the baseline first, then go from there.
As for the varying o2 readings, the factory 02's 'cycle' when not under load (to find that perfect a/f ratio) as well as drop dead after deceleration (all fuel is cut via ecu on decel mode), so that o2 voltage drop is normal, the reason it takes a few seconds to re-register is logger lag
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