The second set of underside photos are almost exactly the same as Tarka, other than the split from a single pipe to 2 pipes occurs closer to the rear on Tarka.
The silencers look the same size as well.
As previously mentioned, with the stock exhaust the noise level as measured 1m from the drivers door by the Castle Combe circuit was exactly as stated on the V5 registration document.
I don't see why fitting side pipes would significantly change the sound volume, but I suspect that the cause may be that the sound measurement device was too close to the car. I'm sure if the sound meter was 1m from the rear it would have been louder.
BUT if the rules in Switzerland say the noise measurement must be from the side of the car then side pipes are likely to fail.
