I experienced something which could be related to your problem with my Akrapovic cans when they were brand new and I rode 300+ hard miles to Wales. It was down to the fact that the sound deadening fibres were blowing out and getting caught in the Db killers, effectively blocking the exhaust. I removed the Db killers and cleaned them, ran the bike without them for a bit, put them back and everything's been fine since. It would suggest to me that in some cases cans, or should I say the fibre matting inside needs settling in. I have no idea what the Db killers are like in the MTC cans and whether they can be removed, but it might be worth a look to start off with?