Generally speaking it is:

stock horsepower X expected percentage gain in IT trim X target power to weight ratio for the class + subjective adders (or subtractors)

I only know the target pw/weight for ITS off the top of me head: 12.9.

So, for my car, currently classed at 2560, the process is:

133 x 1.25 (25% is the default expected gain) = 166 x. 12.9 = 2144!

2144! Let's add in the max adder for torque (100 lbs) and ignore the live rear axle, front struts and drum brakes.

2244! Or, 316 lbs less than process weight. You'd think I'd be leading the charge here.....but I'm not. Why? Because the process wasn't designed to fix EVERY problem, just the glaring ones.

If we are going to apply the process to every car, we are going to have to do serious tweaking to it to avoid major crapisasters.