Originally Posted by nerwyll@trinityautosport
GT is the first version of the exhaust for the M3 by RPI. the differences between the GT and GTM mufflers can be seen by the entrance of the pipes to the mufflers. the pipe enters the muffler at the corner for the GT whereas the pipe enters directly straight into the muffler from the back for the GTM (when looking at the mufflers from the tips). the x-pipe/front-pipes are the same for both applications (and the GTC) for a full system.
Thanks for clearing that up for us!