Millivolts
means more than mixture, to the output voltage.
I'd aim for about 900mV if I had no better way to go. By
the B1S1, B2S1 (front) sensors.
I'd start with 25 degrees and work up from there until
you find KR showing up, then back out. Start safe and
keep track of what you did & what happens. When more
timing stops making a difference you can quit; when you
find KR you can dial it back about 2-3 degrees and be
at about the same power, KR is past the point of best
torque.
As for timing, the stock tune will start around 13*~14* at 1200rpms, peak at 26* around 3200rpms, and drop to 22* from 4000rpms on up.

