Jardine junk...??...Gold nowadays..
I used two gaskets...lotsa sealant and tightened, heated her up..retightened several times..always got a wee bit more...
I had some sealing issues with my stock bike with stock header, and my Viking Header, both were solved by throwing away the old used factory gaskets and scrounging some alloy ones "the banned one" had laser cut. Cleaned ports out well, fitted Viking gaskets and instant seal on both bikes.