I have an SCT XCalibrator and I'm currently tuned for 91 octane.

Using their ExtremeTune software, you can modify the timings your self.

I've advanced the timing 1 degree beyond the custom 91 octane tune and it feels a little more powerful - i'm using 91 octane fuel.

I can advance it antother degree but I'm not going to do that since 91 octane is the highest I can get in California where I live.

It's my understanding that the 05 Mustangs have knock sensors that I would assume retard the engine timing to prevent detonation.

If you advance the engine timing too much do you get an engine light or will it simply record the event in the computer and silently adjust the timing ?