...BTW your Bieber avatar is awesome.-Malone
On porting the exhaust ports, some people say to leave a step on them where it meets the manifold. You may want to do some reading on that.
Use common sense and DO NOT remove any aluminum material directly behind the anchoring area of the valve seat. You do not want to do anything which will encourage/cause a "dislodge" of that seat. The one photo has be a bit concerned....to be honest.
I'll just open the ports by the gasket and leave everything else alone near the stem/bowl.