Do I need a new gasket if changing over the headers?

[rocket rod 7777]

I know this doesnt apply to busas,but some fuel injected engines have oxygen sensors in the exhaust to tell the ecu how its running,so i guess if the exhaust headers are sucking air then it could confuse your ecu?Anyway bottom line is for the sake of a few measly bucks its prolly better to replace them.How would you be if you spent all that time changing your pipes only to find the gaskets leaking and then having to do it all over again.Also good to use a bit of heat proof silastic(the copper based one)just to be sure.
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