Well, your problem could be any of a dozen different things. But I certainly wouldn’t believe an exhaust leak is causing your problem.
But, you’re correct, it is time for you to replace that O2 sensor. On a related note if you do Seafoam the car, replace the O2 sensor AFTER doing it. And yes, Seafoam really does work. It does a great job for what is was intended to do. That said carbon build up may not be your issue.
But it could be the MAF, a clogged cat, or who knows. Have you scanned for codes?
