The RPM's on my 05' A-6 float around between 1400 - 1800. Replaced purge valve,- performed decarbonization , new plugs. Car has 95 k on it. Now the dealer says the next step it to pull the head and clean the valves?? Doesn't sound right to me. The motor levels out at higher rpm and runs fine but is a bit irratic at the lower range. Thoughts??