Automotive News spoke with one of Honda's product planners, and he revealed to the outlet that making the engine capable of lasting "hundreds of thousands of miles" was a key consideration. He said that adding more power would have reduced the overall durability of the engine below what Honda was targeting.
In our experience with the Si, it does feel a bit short on power compared with GTI and Focus ST, but it's still a thoroughly fun, sharp-handling car. It's value-packed, too. We also have no doubt that the aftermarket will add more power to it shortly, considering what's being done with standard turbo Civics right now. As for whether tuning for more power will diminish the life of the engine, only time will tell.