When to change a gasket

[Tkdtim1226]

I installed my new header a few months ago and the company sent the wrong donut gasket. I am finally getting around installing the new one and I am curious if I now need to also replace the flat gasket again. It has not been on for more than 10k so I know it isn't bad from use, but I have heard that when the bolts get tightened on the header, it creates a seal and breaking that seal means the gasket needs to be changed because it won't seal properly. Is this true or can I just change my donut gasket?

 

[henkz0r]

Don't remove the exhaust manifold from the head. Remove the exhaust hangers and you'll have enough play to get the cat off the down pipe and be able to install the donut gasket just fine while it's on the car.