If I've got my GM EFI timing strategy understood, you can advance the base timing, BUT that affects the entire curve. If you advance it 2*, when the ECM commands say 34*, you are adding 2* the ECM doesn't "see".
It won't hurt you down low probably, but up high, you may start running into knock retard, actually losing performance, and you may never know it.
Best way to do it is like you do with mechanical, experiment until you find what the engine likes best. With an ECM, that means chip burning.