[guye]

I was watching an episode of one of those American chop shop series the other night (can't remember what it was called, like those West Coast guys that restore muscle cars or make perverted classics).

Anyway, they were making their own mufflers with ~2 1/2 inch pipes drilled with hundreds of ~10mm holes encased on coarse grade steel wool - maybe two layers - then two layers of chop stand fibreglass mat, then all packed in a 4inch pipe.

Not sure if that helps, but someone else might have seen them and can tell you show it was perhaps...