OK, this is much better!
Some context:
Previously I'd said that the 2bular exhaust was too loud. My car had the 2bular valved exhaust with BOE intake.
The original air box has a vacuum reservoir built in (which allows the exhaust valves to work whilst you're driving). I realised nobody had added a replacement vacuum reservoir, so the exhaust was basically in loud mode pretty much all the time.
I've added a vacuum reservoir in, and now with sport mode OFF, the car is 'quiet' (sounds like the original exhaust with sport mode ON, up until the 4500rpm limit where the valve opens anyway), and with sport mode ON the car is loud. Exactly how I wanted it (and how it should be).
The BOE reservoir was $60 + shipping + VAT + import duty... so I bought a Maserati one off eBay for £20 instead. Slightly different shape but the same thing- a ball with an inlet, outlet, and valve. I think BOE use an EPMAN 47076 but I couldn't find this in stock anywhere.
Installation: very easy.
Pop the BOE intake out (1 big jubilee clip and one other connecting hose)
Bolt the vacuum reservoir down to the old intake mounting plate (note, for my maserati reservoir I had to use a knife to lengthen the slots for the bolts by about 5mm)
Snip the vacuum hose that was connected to the supercharger > exhaust solenoid. (Note, you might want to check your hose is long enough before snipping it. Mine had enough slack in it, tucked away by the solenoid valve. If not you'll just need to by about 1m of hose.)
Attach the supercharger end to the wide nozzle on the reservoir
Attach the exhaust solenoid end of the hose to the narrow nozzle on the reservoir
Put the BOE intake back in.