I got a free muffler delete for my Fiesta ST locally, and so I will measure that when I get home. The guy that gave it to me said that it was the same size as the stock piping. I plan on getting some V-Bands so that I can swap the delete pipe for the muffler as I wish and when it comes time to put a proper catback on I can do it in my driveway. I searched around but nobody seems to know what the stock OD of the pipe is. The supplement said the exhaust is 55mm diameter (2.17in) is that total diameter or ID? I can measure when I get home from work but I figured if someone already had the information on hand I would ask.