Wish I would have seen this before I went through all the stuff with my exhaust, lol. Mostly just because I had no idea the race mufflers were so long until I tried putting them in. I started cutting up my cats to convert them to 3" to try to quiet the car down just a hair and work on some of the exhaust smell. I though the race mufflers were basically just the street mufflers (what I already had on the car before), just 3" instead of 2.5". While they are very similar (same internal design to the muffler, which is one of the reasons I wanted them because I wanted to keep the same kind of sound on my car), they are much longer than a cat back system, so no way to get a cat in there unless it's the primary cat right off the stock manifolds.