I don't know if I can help, but adding how mine works. It is a 2011 non-pp. If I am driving less than 40mph, I can hit the TSC button twice quickly and it will go into sport mode with the same icon on the dash as just having it off. I am not sure if this capability, which is normally only on PP cars to my understanding, came about with my tune or what, but I discovered it by accident actually. .
Update: I can also turn it completely off by holding with the foot on the brake for 5 seconds. I returned my SHO to stock yesterday and I still have sport mode, but not the hill decent manual mode that the tune gives.