If you are by chance installing the exhaust with new gaskets.....you cannot compress them all at once without risking exactly what happened. Those nuts are tightened to like 9 ft lbs.....thats not much
I thought it was 7?
Sorry, I almost typed 7 my bad. Doesnt really matter, this is one of those instances where using a torque wrench is worse than just feeling that its snug. I dont have a torque wrench that I would trust at that low a reading.....and also I have never broken a bolt on a motorcycle when NOT using a torque wrench....lol