i have the carbon oval mtc road legal exhaust bought by Captmoto .
the exhaust is very lightweight and quiet enough with the db killer on but the bike has problem revving at high rpm (kev mode and dna filter allready installed ) . i was about to buy a spare db killer from mtc through e-bay to experiment but they asked 25 + 30 eyros for shipping which is stealing .
anyway i search my garage and found a small silencer a bought a few year ago . the silencer looks like this http://www.ebay.com/itm/Universal-Mo...item4625a8930e
i cut a small part 4-5 cm and plug it directly to the inner side of the existing db killer . i was amazed that the parts fitted directly ! i also removed the metal plate at the begining of the silencer which must cause the revving problem .

now the exhaust is even more quiet and motor revs way better than before .