If the exhaust is part of an upgrade of the ECU (Ducati Performance) there is a significant improvement, and a noticeable decrease in power if the DB killers are added
i run a power commander III ubs , TERMIGNONI cans and spark headers. and sure i am atleast 7% better maybe even 15% and yet i still cannot stay in 6th gear for more than a minute because i live in the real world.