I always thought that the paperwork when ordering an Aero stated that side pipes were not holomogated and were an after-fit but you paid for 'side-exit preparation'.
Maybe that is just in the UK.
I understand you are correct.
Of course, in the UK there is no measured noise check in the MOT, and largely little real control of after market modifications.
Tarka is rated at 87db at 4725 rpm. At Castle Combe circuit they measured 86db at about 4500 rpm. I believe the car has an absolutely standard exhaust.
As there are no silencers after the ones under the running boards below the doors I cannot see that side pipes would make much, if any, more noise.
