That sounds ridiculously good.
Got to be honest, I've never heard of JC Weldfab exhausts. I've got a turbo back Powervalve (formally known as BCS) on my mk5 GTI. Valve is actuated by boost from a line to the inlet manifold. Powervalve are pretty much regarded as the top of the pile when it comes to TFSI exhausts.
It'd be interesting to see what JC can do for the TFSI/TSI. I'm sure there's room in the market for another valved exhaust. I think Scorpion now do a valved option for later cars, but I'm not sure how good it is.
Love the sound of that though. Proper angry V8.