Originally Posted by Scottina06
theres also a catback from Magnaflow and American racing. They are full catbacks
Full cat backs currently on the market delete the factory exhaust valves (that are MDS-related), while axle-backs keep them.
There have been some discussions on forums about what these valves do and the effects of deleting them, but I haven't read anything definitive. The fact that Borla chose to keep them speaks volumes, IMHO...