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The drive belt tensioner noise is more of a squeal or high pitched whine. The purge valve is a low thudding type of noise more like a card in bicycle wheel spokes. Not sure what exhuast valve you are referring to.
It could be a problem with the variable tumble control system. You can remove the hose from the VTCS and see if the noise goes away. If it does then you will need to replace the intake manifold to get rid of the noise.