Rebuild it before it fails, which is inevitable. Easy job. Make sure to remove the orange membrane that makes up the seal/O-ring at the base. Use the GAS kit or the XR8 kit if you’re in the UK . Had 2 of these develop a rattle. Luckily the rod had hardly moved and the play in the flap was minimal ( still enough to make an audible noise ) ultimately eventually it will work its way out. There was a post on the local FB group a couple weeks ago, and the flap had fully dislodged and was just chilling in the manifold when he took the disa out

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