stainless steel bolts on your muffler/catalytic converter.

The more experienced among us know this already. I thought I'd beat the
corrosion problem by using M8 stainless bolts and nuts for my new Bus Depot
cat and muffler. Once they heat up, there's no way to loosen them. I don't
know what happens to the steel, but it sure isn't any labor saver. The heads
just break of when you crank them.  So much for good intentions.