I just got a 2011 Mini S it ran great for about a month and suddenly I keep getting an odd “rattle almost metallic” noise and suddenly the car will put its self into limp mode “1/2 engine light” I have a check engine light and my code reader says it’s the down 02 sensor needing replaced. I have one ordered to put on but I’m wondering if that’s the issue? Would a bad downside 02 cause this? Also I added a can of Seafoam to my tank and that originally caused my car to run in limp for about a whole tank of gas. But once I added crash gas it went away. Let’s see she also has some smoke coming out of the pipe after driving and when you stop at a light and then pull out. Please any ideas!?