After some comparison values for what noise level your exhausts are making. I had my car tested @ 99dB last year at Cadwell Park before a Javelin track day, which makes it too loud to take to either Donington or Elvington and way too loud for Zandvoort, so before I take the silencer apart for a repack do any of you guys have data on what noise levels your cars are making. Will I gain anything with a repack using Acousta-fil?

I usually just scrape under the 105db limits at events, usually by a small amount of under-revving

Alarmingly, that demonstrates just how difficult the NIMBYs are making things these days.
An accurate reading of 99 is actually very good.

A repack may well help, a 7" Can will help, an airbox will help.

Stationary noise (3/4 revs no load) is a lot easier to meet with a bike engine than a drive-by. Retaining the TB's secondary throttle valves helps on my GSXR engines, since these are almost closed during the test. WOT however, particularly with the earlier GSXR1000's (long stroke) has always been a noise issue. OK, at Combe (VERY accurate and VERY strict:

GSXR1000K2, Westfield, foam sausage, 6" full length long factory Can - static (102 dB) - drive-by (106 dB, very loud).
GSXR750K3, same as above, static (101 dB) - drive-by (106 dB, very loud)
Jedi, R1-5VY, factory Can and bike airbox, static (102 dB), drive-by 102 dB.
Jedi, GSXR1000 Turbo, Akrapovic static (108 dB).

Jedi turbo? Bet that's a flyer!

I repacked my exhaust with acusta-fil. It sounded different but i would not say quieter, it sounded smoother.

I dont have facts or data about the difference it actually made.

Flyer...? Certainly was, but wasn't mine, another guy at the circuit struggling to get past the noise test... didn't really matter though, the engine usually blew up before it made it out of the paddock.