So, despite the disappointing leakdown and compression results, the engine is still making good power. That is amazing considering that this engine now has over 30 weekends on it. I like to just run the car on the dyno for about 5 minutes before taking any data. Make certain that you have a strong fan blowing air into the radiator or you will overheat the engine. In first and second gears, the inertia of the engine and gearbox will reduce your horsepower readings.
Third gear is a good choice for getting accurate data.
All of my data is always taken in third gear. By the time you get up into fourth and fifth gears, the drivetrain losses are significant and reduce the horsepower. When you start making data runs, go full throttle at a little over 3000 rpm and run it up to 6000 rpm. Do that over and over until the results stabilize and give power curves that are the same within 1 hp. The five curves in the plot below depict the rear wheel static thrust that is available in each of the five gears.