Bill, I just swapped my stock exhaust on my 07 ST out and went with Magnaflow. While I was under there, I noticed that the fuel tank on the passenger side of the drive shaft is installed so that it would be impossible to run two pipes from a muffler located on the driver's side of the ST, with one pipe branching to the passenger side just in front of the differential. The only way I can possibly see duals being run is a y-pipe situation, where the pipe goes over the axle, and then there's a Y there to branch over to the other side of the differential. However, there are hoses and wire harnesses coming out of the top of the differential and they plastic bed is just above that. I don't see a dual exhaust really happening with the 07ST. It would be much more for looks then performance/power.
Hit the link below. Pic 9 shows the exhaust on the right, drive shaft in middle and tank on the left. Pic 10 shows pipe going up over axle next to the differential. Pic 11 is the exhaust over top of the axle where there would be room to split into a Y and run another pipe over the diff - diff is under pipe, spare tire is on left side of pic.
