Italy is relatively easy on exhaust noise. A year or so back I joined our local SuperStrada where the slip road enters within the last 100 metres of a tunel. I had seen a car approaching in the outside lane and accelerated with a fair amount of noise in the tunel to 90kph (speed limit 70). I turned my head to see where the other car was and discovered a police car right beside me. Naturally I backed off but they did not even take any notice of me.
On the other hand we had a friend who copped a huge fine and nearly had his bike sequestered in Switzerland. I am always very careful when passing through towns in Switzerland.