First of all, I've been browsing this forum for nearly 2 years and am so grateful to have this as a resource. It has been very helpful in keeping my 05 xb12r on the road!

I searched the forum to try and find any posts dealing with a similar issue but couldn't find anything relevant so if this has been discussed before please point me in the right direction.

So on to the issue. Yesterday I was riding and went WOT to pass and noticed that my exhaust noise was significantly louder. I pulled over and inspected the bike to try and find the issue and I saw what turned out to be the O2 sensor sitting against the frame and the rear header. I loaded it up on a trailer and took it home and started removing pieces so I could get a better idea of what I was looking at. Turns out that the O2 bung with the sensor attached was blown off the rear header leaving a fairly clean circular hole in the header. I intend to remove the header and attempt to weld the bung back into place (buy a new header if I cannot) but I'm mostly concerned about what could have caused it in the first place. If I have that much back pressure in my exhaust system could there be some larger issue I'm unaware of?

I have the Buell race exhaust but it does have a small dent on the bottom of the muffler underneath the connection to the Y-pipe, but it doesn't seem large enough to constrict exhaust flow. If anyone has experience with this sort of issue or could help provide some insight I'd be very appreciative.