I remain amazed it passes it's MOT (next week)
95db?!
I like
the description of allowable noise: Test procedure
The exhaust system must be free from serious leaks or advanced corrosion. The entire system must be securely fixed to the vehicle as intended either by using exhaust mounts or the common rubber fitting mounts. The exhaust system must have the required number of silencers for your specific make and model of car. Your vehicle
may fail the MOT due to noise levels if deemed to be excessive by the MOT inspector."
so hope for a petrolhead tester! 
So given that the side exhaust is an option to the standard factory fit, you could apply this MOT clause:
"A silencer in such condition, or of such a type, that the noise emitted from the vehicle is clearly unreasonably above the level expected from a similar vehicle with a standard silencer in average condition."
& point out that it's
no louder than a piano 
Will
