Yet another reason I'm glad to not live in NJ.Law went into effect on July 10 and there has been some enforcement.
A letter from Maine SP Traffic said that essentially if you not attracting their attention you won't be noticed. Translation I suppose it that the if you are not an idiot don't worry about it.
Just FWIW, my wife had a dead stock 1989 900 (non turbo), and it failed for an allegedly loud exhaust. This nit-wit beech tagged me coming in every time till I produced a letter and a business card from two different muffler shops indicating that I did not need nor was it an altered exhaust. When I requested a supervisorand produced the papers the "noise" magically disappeared.
This was not a state employee, this was a Parsons (private sector), "inspector".