I am not sure how the measurement is taken at Goodwood (perhaps others do?) but at Castle Combe , the scrutineer told me to rev the car to 4000 rpm and hold it there for about 10 seconds. My +8 (Rover V8 not Aero) was so far below the limit it hardly registered.
My experience of the Aeros on side pipes is that they are rather noisy on the overrun , and when lifting off , when at constant throttle they are normally less obtrusive.
There may be an app you can download for the phone and then use that to check?
