Because Activision never remastered Blur , the current PS4 version is an unofficial, community-created homebrew port.

PS4 backwards compatibility with PS3 games (stored... - Sony

Let’s address the elephant in the room. The game was developed for the PS3 and Xbox 360. Due to licensing issues with the real-world car manufacturers (Dodge, Ford, Audi, etc.) and the licensed music soundtrack, Activision has shown zero interest in remastering or re-releasing the game.

Open the emulator (use the "Plus" version for better PKG support). Install Packages and select your game/update PKG.