as with any modified engine, the components need to be able to work together. If you want the most out of your engine your going to have to find out what works best for you and what kind of riding you do. As with any power modification it will come with a price, as in longevity of your engine. running a high compression headgasket already has an effect on engine temps and running a timming advance together with this could bring you to the edge of what your engine can handle on pump gas. If you planed on running high octane im sure a timming advance would be a good option for more power but if not Its hard to say it would handle it. In your case I would say ditch that high compression headgasket and get the head modified. this will still raise compression but also optimise your combustion for more reliable power.