E85 Spool AFR Transition
 

So I have read that people usually tune to 12.0 gasoline AFRs on e85. My questions are:

1. When does one transition to 12.0 AFR from spooling? Different turbos charge different amounts of air at given psi, so how do you know when to shoot for 12.0? I know it is before peak torque, but how soon?
For example my green hits 20 psi at about 4k RPM. Should I be at 12.0 AFRs then? Currently I’m at 12.0 at around 3-3500 RPM.
2. What is your AFR during spool with e85?

Thanks.