Now that should put some minds at ease. Very informative Cyrus.
This means that the ATMO blow off valve is LEGAL provided it does not make "excessive noise" and or cause the emissions to increase or blow smoke. ????? Not 100% sure but that's how I understood it.
And it also means that you cannot be booked for just "having" a blow off valve, they must prove that it is, indeed, excessively noisy.
It is also my understanding from reading the above post that you cannot be booked for your tyres "chirping" if it was unintentional. Is this correct?