Like Turboguzzi says...
The ideal situation after mods is to put it on the dyno, and advance untill power does not increase anymore. And them maybe back-off 1-2 degrees for safety...
Thats your max brake timing point which means optimal ignition point. If you go past this, you just generate lots of heath (holed pistons).
So, do NOT just put your ignition at 40 degrees at WOT because you think more is better.... A lot of people do this and hole one of the pistons.
Leaner mixtures and slight throttle openings (so low cylinder filling or VE) require more ignition (up to 50 degrees) then full throttle (often 32-35 degr. for older bikes). Thats what a TPS or MAP sensor is used for and you get good fuel economy by doing that.
Check out the graph in the attachment.