I'm throwing a 0707 code which points to rear O2 sensor, but there's what sounds like an exhaust noise coming from the EGR or EGRC area that I think may be related. The FSM troubleshooting process for the rear 02 sensor mentions checking for intake or exhaust leaks, so I'm thinking something may be hosed up besides the 02 sensor. The noise I'm hearing sounds like exhaust and some backfire "burbling" when I rev the engine and let it come back to idle. Definitely not a normal engine sound. I've done the vacuum test on the EGR and it appears to be OK. Haven't done the the FSM test yet on the EGRC, so don't know if that's functioning correctly. I don't see any obvious external leaks. Any ideas?

bump..

same problem. when the car is cold, mine doesn't do it. but as she warms up, the noise gets louder. under regular acceleration, there will be a loud noise, as well as the 'burbling' noise while the engine comes back down to idle.. kind of sounds like its coming from the back of the car to me, but its hard to tell from inside the car

The gasket between the EGR valve and the cylinder head may be blown out or leaking. Also the metal tube that is attached to the egr valve may be plugged up solid.