Legal reasons, certain law in Europe regarding loud pipes are getting stricter and stricter. I think the limit is 77dB at the moment (euro5). Certain roads in Austria are now even closed for certain motors independent of their exhaust because of the noise. If you own any of the follow motors then those routes are closed for you even with stock exhausts
Aprilia
RSV4 1100 Factory
TSV4 1000 RR
Tuono V4 Factory
Tuono V4 1100 RR
Ducati
Diavel 1260
Hypermotard 950
Supersport
Multistrada 1260
Multistrada 1260 Enduro
Multistrada V4
Panigale V2
Panigale V4
Panigale V4R
Streetfighter V4(S)
Harley-Davidson
Iron 1200
Sportster 1200 Custom
Forty-Eight
Superlow
Roadster
FXDR 114
Honda
CBR650R
CB1000R
CBR1000RR (SP, SP1, SP2)
Indian
111 en 116 modellen
Kawasaki
Z900
Ninja ZX10(R, RR, SE)
Ninja H2
KTM
Duke 890
MV Agusta
Brutale 800 (alle versies)
F3 800
Superveloce 800
Brutale 1000
Rush 1000
Suzuki
GSX-R 1000 RR
Katana
GSX-S 1000(S en F)
Triumph
Bonneville Bobber
Daytona 765 (LE)
Rocket 3
Thruxton TFC
Street Triple R/RS
Tiger 1200
Yamaha
YZF-R1 (M)
YZF-R6