The various tracks have different levels of noise limits.  If like me you have a louder exhaust than OEM then you maybe on the limit.  I am going to drive to my local track (brands hatch) and get the car tested so I know if im OK.

I know that Brands Indy is 101db which be pushing the limit, so maybe I need one of these:

Merlin Muffler

I dont have any experience of these.  Do they limit your power as well as the noise....