The difference between the tunes is almost entirely timing advance and in our experience the difference between these tunes is about the same as the deviation we might see car to car with the same boost/timing - so it's kind of a moot point to try to be more precise, IMHO. As others have said, a pulley/tune (from Torrie) is about a 100HP adder - and there is NO characteristic change to either torque or HP curves (other than the magnitude) - nor is there ANY adverse effect on any drivability attributes. Same starting, same temps, same idle, same tip-in, etc. In our 16-years of modifying GT's, I'd say that this is singularly the most popular modification made by owners.... and for good reason.