Went to the dealer with a P2A00 code (Bank 1, Sensor 1 O2 performance issue). Sensor was toast, so it got replaced, along with oil change and such. Now there is a strange "clapping" noise when accelerating hard. Seems to come from fight under the driver's area. My guess is that it is an exhaust leak at the cat/CBE flange.Of course the code came back, along with CEL. Any other ideas before I rip the dealer an new ******* for not fixing something so basic?