[AtomicLabMonkey]

I don't know what temp the spray you've got is rated for, or how hot the manifold casting gets during operation, so it's hard to say. My concern would be goop melting away and doing something to the turbo, but I dunno if it would be an issue or not. You might want to try finding a copper crush washer that will fit the bolt instead, to be your sealing surface, instead of gooping some spray in the threads.