What do you ride? Combe's noise restrictions are legendary. Stumpy can r6 and gsxrs can forget it as can k5 1000s. The sound reading is taken so close to the pipe it picks up the air induction. The more you baffle the can the louder the induction. I've seen alot of sad faces at combe track days. I can have a word with Emma in the office and see if your bike is on the "noisey list" if you like.

Also keep in mind alot of teams test at combe for the IOM TT because it's the bumpiest circuit in Britain and also one of the fastest.
Don't let this put you off but it's better to be armed with all the facts so you can make a descission.