I bought a 04 C230 supercharged,from the original owner,156k miles,all dealer kept up.I got a great deal because the lady owner stated that it started to burn some oil,1 quart every 2000 miles and ocassionaly a little blue greasy smoke at start up...anyway,car had the pcv recall done by Mercedes at about 80k.I don't know if the pcv hoses and screen got clogged again or maybe has some carbon buildup on the valves.Runs great,no check engine,no ruf idle,maybe some carbon cleaner thru the vacuum hose will help,or kill the cat converter...?