I have Litchfield Stage 4 with 90mm (I think) Milltek Sports exhaust.
I was at Bedford last summer and sailed through the static test at 93dBA. Problem was drive-by which I think is 98dBA. I was black-flagged twice. The first time I was told not drive anywhere near another noisy car (especially my mate in another GTR) because the cumulative effect would alert the noise police, and the second time I was told I would have to back-off if I was anywhere near the noise sensors (it was up to me to work out where the were). I was actually quite lucky not get to sent home, which would have been a complete waste of a 500 mile round trip and an overnight stay in a hotel.
Now I do understand that there may be a few pensioners who don't go out to work during the day, who have bought a house near an airfield and expect absolute silence during the day, but I do find it bizarre than they can run track-days there and you can pass a static noise test, but if you drive near someone else they will throw you off?
Don't want to put you off mate but I will be giving Bedford a miss from now on, which is shame because it's a high speed circuit and great for GTRs.