My wife was stopped today by the police saying our RS4 fitted with a resonated valved Milltek exshaust was too loud and to get it sorted. ( the S button may of been on) No ticket was issued but maybe next time, so are all after market exhausts illegal ? unless original Audi replacement
SHOCKED, yes it is louder than standard but not compaired to some of the cars that come past my house, so started looking in to the law
SHOCK HORROR

The offence I can come up with is "use a motor vehicle with an altered silencer/exhaust system" this is reg 54(2) con & use 1986, sec 42 of the RTA 1988, sch 2 RTOA 1988.

Basically the offence is self explanatory and from the officers point of view the "points to prove" are simple, they are date & location, use on a road a m/v fitted with exhaust system/silencer altered to increase the noise made by the escape of exhaust gases.
So it is quite easy for them to stop you, see that your exhaust is not standard/original and give you a ticket and as long as people cough up the £30 they will carry on doing it. This is a "grey area" and because of this some forces do not use this particular piece of legislation anymore.
However in the statement of facts it clearly says the exhaust must be "maintained in good and efficient working order" & "has been ALTERED in that it increases the noise made by the escape of gasses". So replacing the exhaust with a pattern or replacement is illegal, yes or no, most aftermarket exhausts on RS's are slightly louder/deeper sounding than original BUT if it is within the legal db limit and is being sold by companies as "road legal" I dont see how any court could convict.
But how do they prove its louder with out taking a reading from the same car in the same place with a standard and milltek exhaust fitted, I am sure they have to prove youre guilty not the other way round.

There tons of info on this problem on the scooby sites.
ADVICE PLEASE
Steve