Hi Modrunner, Here are my updates to your qurstions.
Sound: Slightly quiter then Stock.
Perfomance: Subjectlively you are loosing a few horsepower compared to Stock.
Apart from the Look and less weight the Overall perfomance is a bit dissapointing.
This is due to the matter that the DB Killer has a smaller diameter then the stock silencer and in addition there is a Steel cap at its end which blocks the free flow of Exhaust gases.
In order to get sound and Performance to stock Level I removed the metal cap and drilled a few holes into the db killer pipe. After this Measurements I am quite satisfyed with the overall Performance. Sound is different then stock.