Very useful to know
So thats a 30" long tube which is capped at the end?
Many intake systems use such a thing to reduce induction noise - I think the D3 S8 has it in both intake tubes iirc. Never seen it used on an exhaust before but it makes perfect sense it would work there too.
Could it be that its only of real value on V8s, hence popular in the US but not here? We're not the usual target demographic of companies like Powerflow I suspect but I would think the likes of Milltek would understand it.