what's the best method to test for that leak?

I hate living in TN. Back in Houston I never worried about emissions. Just put $40 under the floor mat when inspection time came and passed every time!! Haha.

 

So if you don't smell fumes or rotten egg smell that's a start. You need to drive the car and full operating temp and then look underneath while its idling. You need to get the codes one way or the other. It's a complicated vehicle, you can't really treat it like an old beater. How is the car running? Smooth? No real driving issues? Fix the O2 sensors and go from there.

 

MattyG,

You have a good point. Also, he can go to any good muffer shop and if the mechanic there have a lot of years experieces in cars, he can found the leak on your exhaust before you buy the O2 Sensor. Is the cheaper way to check if your exhaust system have or not have a leak. Probably the muffler shop no charger you for check that leak. Again, probably or maybe a few $$ that is cheaper to start buy a O2 sensor, the mid cat pipe or the full cat.

 

Drives the same as before the light was on. But since I've bought the car I noticed when coming to a complete stop or rolling in traffic the car will jerk. Like someone hit me from behind. Wonder if it's linked to this.

 

Yeah that sounds like a separate problem. I would check the transmission fluid first for level/color etc. As mcon says, an exhaust shop is your first stop, then potentially a Toyo dealer to do a Techstream analysis of what your fuel/air/ignition is doing.