Your ashford cat gasket was supposed to go all the way around. Glad you fixed it. You should be able to access everything from the flue outlet without removing the cat.
now you tell me. so now I know how to take the thing in and out. I think It was easier to remove it take it to the shop then to lug my shop vac in the house. The only gasket i saw when i removed it was on the bottom. Is it possible the gasket desintagrated?. Unless Im on drugs there was only a bottom gasket