Just to elaborate on what KJ said...

A port and pollish should be one of the last things you should do to a motor. Only after you have completed your setup should a GOOD PnP be performed. In my opinion, a good port and pollish should only be done by someone with a flow bench, who can show you the flow improvments. Portflow comes to mind. Remember, you get what you pay for. Especially in this case. 250 dollars for a PnP from some machine shop down the road will not be what you're looking for. Even just a gasket match, or a "cleanup" can completely fuck the flow of the head up. Be CAREFUL of where you get this done.