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I recently retrofitted a sound generator pipe to my 2.2. It sounds great, but I can't work out whether I prefer it with no foam, small foam only, or large foam only. (my wife prefers it to make no sound at all, but she's not driving it!).

The problem is, with anything less than the large foam piece in there, I get a vibration which happens at revs just above tickover, just for a split second. It's annoying. I think it's coming from inside the diaphragm section, if I tap it with my fingers, I can replicate the sound. It's not the spring clip, or where it attaches to the top of the engine.

Has anyone else noticed this? Or is it just me?

I read your post and it seems like I’m getting a similar sound but it could be something else inside the car. Will investigate further as I really don’t like rattles and whatnot.