I have never driver an autocross and do not know much about them but isn't an autocross more of a driver's race? In an autocross the driving more complex than on a nice straight open road. If one driver has detailed knowledge of the autocross course and the others drivers do not, the driver with the detailed knowledge of the course will have a tremendous advantage over the other drivers, more than just horsepower could overcome. I do feel with equal drivers, even in an autocross the SVT would beat a 2.5 SE with a five speed.
The extra 25 to 30 horsepower of the SVT is more than enough to cancel the extra weight (100 lb?) of the SVT. I have noticed that the peak torque of the SE comes sooner than the SVT but the SVT probably has a very flat torque curve. Meaning that the SVT?s torque is probably close to the SE at the same RPMs but the SVT?s toque goes even higher (by a couple of ft-lbs) at higher RPMs and while the SE?s torque falls off. This is what I think, I am not sure of this. I am sure the SVT is faster than the 2.5 SE with a five speed, even in an autocross (with equal drivers of course).