I'm trying to suppress a reverberation - It appears when the car is in "D" but not moving, held by foot or hand brake.

I know there have been other threads about exactly this type of noise, but in my case I'm pretty certain it comes from where the small vertical metal pin on the rear of the engine cover locates in the oversized corresponding hole on the rear face of the air filter duct. The two components touch and make a noise, which is annoying me.

I am confident that they're not meant to actually tough, but should perhaps have a rubber buffer or grommet that would slide down onto the peg and thereby isolate the two surfaces from each other. Perhaps it was never replaced after a service.

Is there such a thing, and if so what is it called and what is its part number?

In the absence of the real thing I'll make one from rubber tubing and a cable grommet.

Well, after speaking to the very kind gentleman at Duckworth's I know the answer. There is indeed a fitting, internally threaded, that provides an attachment between the two components with a bit of silicone or something to provide a bit of slop in order to control vibration. I don't know what it's called, it comes with the air duct component and isn't available separately.The duct costs lots of money, of course, and the Yorkshireman in me

A quick squint at my engine cover confirms that it is indeed threaded on the lower part of the vertical metal lug, so I'm going to have to source an internally threaded screw (or do I mean very long nut) that is of dimensions suitable for padding out with some rubbery material. It my well eventually go down the route of rubber sleeve, cable grommet and that good old standby the cable tie.

I shall ponder this and experiment.

Threaded sleeve rod is what you are after. Loads of sizes/length/threads on eBay. FL2 Metropolis, Loire Blue, ebony/ivory