Follow up to Oil on threads of 7-8 plugs. Intake removed. Valve issue? Help

[stotzbotz]

Would it be safe to say at this point in the break in that if the other plugs are not showing any signs of oil on their threads that I should just take off the head in question and have the issue addressed that is currently happening on 7 and 8 valves? I guess this is my fault as I gave the shop the heads and told them to check them out, fix any problems and so $350.00 later I thought that they would have taken care of what needed to be done. When they had them and called me they stated that 2 exhaust valves needed to be replaced but everything else looked fine. I am new to this level of work on an engine so I might have not been specific enough.