Not sure if the diameter will allow them to be fitted to your existing system. However, my 50mm Termis come in at 102/3 depending on the tester and 99 with the db killers. I would imagine the 45mm is not as loud. Most circuits are 105 apart from Oulton at 102. You do have quite days a 98 sometimes but this is usually stated on the booking form.
Yep the 45mm Termi Cans from a 748 will fit the 45mm system found on the 998Bip But no idea of noise levels as my 998Bip motor has been upgraded to a full 50mm System fitted to it