Unfortunately there is a lot of double standards when it comes to the law - ADR, EPA, etc. Prime example is noise pollution. Noise is noise and should apply to all types of vehicles and parts thereof. Cars, bikes, and trucks all have different noise pollution levels and are not on the same restrictions. Even within each class of vehicle there are differring categories. Futhermore, noise pollution from pods does not equal noise pollution from exhausts.
Many of the defects are issued at the police officers discretion, so what saliya said is very applicable. Don't be a dickhead and you might not cop a dickhead attitude in return - and a whole lot of fines/defects.