I never use ET to calculate HP. ET is hook and MPH is horsepower. Way too many variables in ET to use it for an accurate HP calculation.
When I looked at Pittsburgracers numbers I noticed his ET was really good for his MPH. Now that he posted his gearing and gear box it makes more sense.
For any given MPH there is a minimum ET. The closer the two are, the better it is.
As an example, a car that runs 12.00 at 140 didn't hook but made an *** load of power.
If the car went 12.00 at 90 you know it's down on power and hooked up.