Yeah mine did the same thing about a year ago, I think mines the Catalytic Converter, I didn't feel like dropping that much money into my car. So I just paid the $300 for a "certified" tune-up and they had to pass me. Altho when i came back in, for the second time, they had to check if I actually got the stuff put in, so I suppose that takes out giving a gas station $20 for the papers saying I spent $300 on a tune-up, oh well...btw, it still works for tint! give'em $20 and they'll look the other way on the dark tint.
So if everything dosn't work, get the tune-up.
Good Luck