When I got my used 2006 Mustang GT, it came with a custom Flowmaster exhaust. For a while I had been trying to figure out what series Flowmasters they were based off a bunch of numbers on the muffler. Turns out they were all just various patent numbers I was looking at. Today I got under the car and took another look and found the right part numbers. They are 952566-R *Right side and 952566-L *Left. They are part numbers that are part of the American Thunder system. But I still wondered what actual muffler series they belonged to. So I called Summit Racing and they cross referenced them to 50 Series Delta Flow. I have to say at WOT these mufflers sound bad ass. But I think I am going to replace out the mufflers with some Super 44s. I had Supers on a Pontiac GTO I got rid of and it sounded super bad ass. Does anyone think that would be a downgrade going from 50 series DF to Super 44s?