Keep in mind this is a race motor. However, the flat-6 used is very similar to what Porsche GT3's for street duty would see although obviously with lower redlines and associated component changes for racing. That said, what applies here woudl also apply to the very similar 996 GT3 3.6 liter flat-6 GT1 racing block based street car.
The baseline shows 326.4 peak horsepower at the wheels. After the E85 tune this rises to 371.9 horsepower at the wheels. A gain of 45.5 horsepower as shown on the Mainline Dyno. Those are impressive gains for E85 and a tune.
The baseline dyno shows the engine revving close to 10k rpm which drops in the tuned graph as the gear ratios also were changed. This does affect how the curve is displayed on the graph. Regardless, these are impressive results on what is already a high strung motor.