I used a Dremel tool to port the throttle body. I removed most material from the outer edge to flare out the air entry. To avoid issues with idle control, I made sure not to remove material too close to the butterfly valve. The air passage for the crankcase ventilation is a massive air block, so I shaped it more aerodynamic using chemical metal. I intentionally left a rough surface, as the physics says so
After taking the picture, I also decided to bypass the coolant loop, so I cut off the coolant hose connectors. The coolant loop is there to prevent the butterfly valve from freezing in cold weather, but that can only happen in extreme conditions (I drove my Subaru WRX in -35°C (-31°F) with the same bypass, and had no issues).
Stock throttle body for reference
Update: After 4 years, I've had no issues with the ported throttle body. Pickup on acceleration is sharper, which was the goal.