My 2006 Highlander 4cyl. has had the check engine light coming on for about 2 years now. I cannot remember the code right now, but it says bad emissions from the catalytic converter. I replaced both of the oxygen sensors and the same code keeps coming back. So, I guess it is time to replace the catalytic converter. On this model, the converter is attached to the manifold, so the entire assembly has to be replaced. Have any of you replaced this assembly? If so, how difficult was it?