Advancing the timing

[Derrenbacker, L. Jonathan]

I have a 91 sentra se-r. I want to advance the timing for the maximum power
on 93 octane gas.

First, I heard that theres a secret to get the computer to accept the
change. Is that right? Whats the secret handshake?

Second, what timing do youall recommend? I've heard 17degrees and I've heard
20 degrees.

Thanks in advance.