Advancing the timing from the stock settings increases power but also increases the possibility of detonation. Factory settings are "safe" to avoid warranty replacement costs. If you run premium gas you can jack up the timing a lot but then if you fill up with regular the engine will probably ping on acceleration (detonation). Advancing the timing is about the first mod you make to pretty miuch any performance automobile. Unless you advance it too far and cause detonation, there is pretty much no downside to it, except you may have to set it back to stock to pass emissions. Advancing the timing increases combustion temperatures which promotes the formation of oxides of nitrogen. (NOx) It also makes your engine run a little hotter. However if you do advance it too far you could melt a hole in the top of a piston or cause other serious internal engine damage. Detonation is no fun