Have to agree. For a little bit of extra noise, it’s a disproportionate amount of expense, a lot of work, and when you take into account having to reflash ECU’s, destroy warranties, and render insurance policies null and void, a fair amount of risk.
A car that’s supposed to have an OPF isn’t just illegal due to the OPF being missing, it’s also considered unroadworthy without it, despite your bolting it back on for MOT time. An unroadworthy car is an uninsured car, so if you have an accident, if your car gets stolen, or if you get pulled over for some minor misdemeanour, you risk losing the car and much more besides.
This begs the question, why not buy a different exhaust pipe? You’ll get a nicer noise and it’ll still be legal. Declare it with your insurers and it’ll still be insured.
Even if you can’t find something off the shelf to suit your desire for dB, you can always have something made. I went to Hayward and Scott years ago for an exhaust system, it was custom made for me, and came out around 15kg lighter than the stock system. Sounded ****** marvellous.
