
No surprise really EMD cos its the two centre boxes that muffle the noise. The back box only lowers it a bit more and changes the tone. I spoke to the test station yesterday and they consulted their testers manual, even showed me where to read it online and as long as the fumes are released outside of the perimeter of the vehicle, the noise level is below a set limit (in fact its quite a high one anyway) and there are no leaks it will pass the test.
According to that a back box is not compulsory but might be on some vehicles if it affect performance by providing back pressure to the system.
With the back box off mine the only difference was that it changed the tone and hardly raised the niose level at all. I did that purely to see what it would be like for my own information. If I had used thrashing revs it might be a different story but I am not a boy racer type anyway.
At the end of the day if the back box is a lot more expensive than a couple of extender pipes then it might well save someone some money if they do not mind their vehicle being no longer original. Everyone to their own choices but to be safe get it checked by someone with a decibel meter! By the sheer amount of blarting exhausts already used by many of the younger generation and the fact that they get away with it most of the time shows that the police are not that interested anyway. I suppose they only act when some pratt of the boy racer type is causing a regular nuisance and joe public complains.
