The factory exhaust on the 4--series V6 motors has the same log-manifolds + integral catalysers to help pass emissions tests. Larger-bore downpipes (Y-pipe) - up from 51mm diameter to 60mm! The final downpipe to the silencer is 76mm - up from 63.5mm. All to reduce the exhaust back-pressure which might help extend the life of those integral catalysers - might.
The factory valved exhaust silencer has a 76mm bore when that valve is 'open' and a 48mm diameter by-pass pipe when the valve is 'closed'. I've always found a 76mm bore exhaust very difficult to control noise-wise. The correct bore for the 2GR-FE V6 supercharged motor is 70mm - I have customers with over 550bhp running that bore. Too big (76mm!) means lost boost - lost boost means lost power.
So - the 2bular Evora 400 TRACK exhaust has a 70mm bore through the main silencer and two noise-cancelling chambers to help reduce the decibel count. It is a real pain to fabricate and weld internally - but it works very well. I took the opportunity to fit a short resonance silencer between the downpipe and the silencer - every little helps! Plenty feedback from satisfied customers. For the really strict tracks here in the UK and EU I recommend the additional tailpipe silencers. These have been developed over the years to really help the keen trackday enthusiast. Originally 250mm long, they now stretch to 350mm long and their tailpipes have been lengthened to bring the sound energy closer to the tarmac and spread it out more efficiently.