Quote:
Originally Posted by wrh3
I would think the cats on the OE headers/exhaust manifolds generate more heat than headers. I am installing headers on my car right now and had plenty of room and access to go ahead and replace the passenger side mount bracket bolts with BMW MotorSport 10.9 bolts and Nordlocks. The OE bolts were all tight and none were discolored as some I have seen, my car is a 07/2007 build. I think the issue with the bolts is related to a process where they were exposed to excessive heat at some point during assembly after reading the TSB, and that is why we have not seen this issue with the E46 M3s.
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For what I know is because of heat expansion and not being able to take the load the headers put them thru, and with cat can be hot in there but depending on the headers you use you make closer to the bolts.
But again this is just something that goes around and not a definitive answer to the real cause.