New stainless steel exhaust issues - idling too high

[parsasm]

Took out the Manifold, put some instant gasket from halfords on the copper gaskets put the manifold back in and pushed it in nicely. put everything back together and now shes firing up like a beauty.
before the ART can made the bike idle at 3,000 rpm and now its idling fine. The bike no longer "hoots" or rattles.
i may have to get it checked if its running lean, but everything seems good sounds very thick and meaty with the art can
many thanks to banner001, helped me out allot
thanks