As I said in post #8, I removed mine completely and replaced it with the stainless "cone". The gasket was supplied in the kit I purchased.
The vacuum lines were also removed right back too the modulator and the open ends were plugged with the little rubber bungs.
The actual blanking plate was fitted on the opening in the exhaust manifold. All the required bolts were replaced, 4 on the cone and 2 on the blanking plate.
Just to be on the safe side, I did apply some exhaust assembly paste, although a thin smear of "Gun Gum" will also work, to the blanking plate to form a good seal. Be careful not to apply too much paste because once it's hardened, any excess could break free and end up somewhere in the turbo.