I tried stock mode on 8.5R yesterday. The boost timing was set to 12 degree, I noticed that power was increased but ESC was getting hot easily. Then I set boost timing to 9 degree which will be more or less like Modified mode.
Agree ahhh.... racing events have rules. Stock motor racing allow more people to join in with similar settings so as to test the driver's skill more than just high power cars. With brushless and lipo development in recent years, the limiting factor is now less on power and speed but on other factors such as skills and car tuning. Everyone can easily configure a very fast car but not necessarily have the skills and a well balanced car, as such the racing standard (enjoyment) is somewhat less with just high power cars.
Similarly, one can put in rocket engine in real F1 cars but the race would not be very good to watch perhaps. . ..