These have always struck me as a good idea.
I discussed with them about doing something with my +8 exhausts, they reckoned that would be doing something for cars at some time but nothing has come out yet.
(I always smile at the thought of someone building up a successful business based on the name of a fictional character and then, at some stage realising that they spelt it wrong)
Our Abarth came with a by-pass exhaust as standard, but
BTB Exhausts have developed a similar after-market version and I quote from their post on another DG:
"
The BTB Abarth 500 by-pass systemThis exhaust is made from 63.5mm T304 tubing throughout, and uniquely features a boost operated valve which allows the exhaust gases to by-pass the transverse silencer thereby minimising back-pressure in the exhaust and allowing the turbo to spool up more quickly for maximum performance.
Whilst cruising on part throttle, the valve remains shut thereby activating the chambered silencer ensuring that there is no intrusive boom inside the car. The by-pass valve can be easily disengaged if the car is used at noise sensitive track days.
The price of this system is £899 including VAT, which for a limited time only includes free fitting at BTB's premises in Northamptonshire or free delivery to mainland United Kingdom (excluding the Scottish Highlands).
A simpler system without the valve is also available for £750 including VAT."
Although this particular exhaust is designed for a turbo engine, there is an actuator that is operated by exhaust pressure and thus is an active system which prepares the exhaust for more flow. Something similar is fitted to Aston Martin's too (which are non-turbo) and therefore, they should be able to do a tailor-made exhaust for a Plus 8.
They may be worth speaking to on the phone, if you do please ask them if they can do something similar for an Aero SS?