the timing is computer controlled.
So you haveto get the ECU to do it. That said, go and find the "high altitude" CPS, it's supposed to advance the ignition timing a few degrees.
Why do you want to advance the timing?
Using a "high altitude cps" did cross my mind until I found a picture of one. The sensor is simply repositioned on the bracket. I also thought about slotting or elongating the mounting holes to allow for adjustment. As far as why?..well just looking to squeeze some more ponies out I suppose.