After new plugs & wires installed, the a/c starting making a slight noise along with slight engine hesitation about every 30 to 60 seconds only when driving, not idling, next day check engine light came on, mechanic said code was for catalytic converter (which was replaced 2 yrs ago). Mechanic did not offer any remedies except to go back to converter installer. Does any of this have to do with the tune up?