I didnt replace the header gaskets. The header stud nuts were not very tight. So I took a chance that they would seal and "crush" a little more.
They did seem to seal ok.
My only concern was noticicng how deep the 02 sensors go in the pipe and taking up so much room for exhaust to get by.
I guess its ok cause everything works as it should. Should have been a bigger pipe to compensate for the bottle neck.