DCiFound
SEAHAWKS!!
having someone diagnose it will give you the same result. Diagnostic is just a code reader that determines the issue. They will tell you the same thing you already know.^^ Did this ^^ Doesn't sound like a leak anywhere. So there's that checked off. Think I can safely say that unleaded fuel was always used ha. With all these possibilites I might just have to pay up for a diagnostics test and get a for sure answer instead of waiting time and money on guess and checks..
Usually when something like an o2 sensor or cat fail, the reading will pop up multiple issues. Cus they both tie in together
The best thing to do is go the cheaper route...o2 sensor. If its your cat, then at least you have a new o2 sensor