I recently installed my invidia cat-back exhaust system, and upon removel of my stock cat-back i found a donut looking washer like thing next to the flang closest to the cataliytic converter, so what my question is is do i need to put this donut looking thing back or not?. My friend who helped me install my cat-back said i do need it or else i will have an exhaust leak. So what me and my friend eventually did was modify the stock gasket so that the donut looking thing would hopefuly stay in place and not fly out the muffler. If anybody could provide suggestions or answer i would much appriciate it.

Thanks

 

That doughnut gasket stays on the downpipe side of the flange. There should be no reason for it to "fly out of the muffler."

Yes it should be there, and if you had asked any of the Hawaii guys we would have helped you.

 

Thanks for the help, next time ill just ask you guys since you are the only one who responded anyway