I have developed an exhaust leak around the flange of my exhaust manifold, I replaced the exhaust manifold gasket with a new Fel-Pro about 2 months ago. I noticed when I put it all back together that there was no flange gasket. I tightened everything down and there seemed to be no problems. My question is should there be a dounut style gasket used on the exhaust manifold flange? Also I am looking for reasons why this would just start leaking out of the blue. Thanks for any help.