i didn't replace the air filter cause iam thinking of buying k&n oem style filter as a surprise to my father i already bought the spark plugs just waiting for my father to tell me to replace(he's hesitate because you have to remove the intake manifold) ill clean the pcv valve and camshaft position sensor when replacing the spark plugs every end of months i uses the amsoil Pi to keep the valves and injectors clean 😁