I had the same problem not long after I installed the tyga tail. To me it appears to be the way it is mounted to the subframe (on two welded on nuts) which give no contact to the rear face of the regulator, therefore no way for frame to act as any kind of heatsink. I moved mine on both track and road bikes so that the rear face mounts up against the subframe and cut a section out of the undertray to allow air get to it.

Better still would be to install some kiind of proper heatsink under the regulator (maybe just between the frame and rectifier).