Wonder if the muffler is blowing carbon all over? I'm sure condensation would make it sludge up like that after being neglected
Welcome to the forum! Looks like you're in Italy? Is there a redline in Italy?Sorry for the late reply, but I’d like to drop in and say that it could be a buildup of carbon or dirt, but it's hard to say for sure without seeing the video. Have you tried cleaning it off to see if it comes back? It could also be worth getting a mechanic to take a look at the exhaust leak to see if that could be contributing to the issue.