Welcome to the perma-in grin family! The shifting could be based on how hard you push it. There is also a W / S button near the shifter. W is winter and it will start in second gear. S is your performance setting. I wouldn't mess with the alarm. These cars have an incredible anit-theft system. A good muffler for the SRT might be a Hooker Aero Chamber (1 in / 2 out) with your stock tips or custom ones.