Is my catalytic blown?
The car had P0420 code before and taken cared by an eliminator spacer on the 2nd 02 sensor. Maybe it's a sign that the cat is about to go...
So after taking the car to a few track days, I found a noticeable rattle from the exhaust. The rattle sounds like tiny metal pieces hitting, and the rattle appears whenever the rpm raise or drop while in gear, but goes away when rpm is held by steady gas.
I had the rear diffuser removed and found everything secured and no heat shield touching the exhaust; however, I can hear the tiny metal pieces sound when I hit the exhaust pipe.
Any guess? Could this sound be normal for the honey mesh inside the catalytic become melted or broken?