Complex sentence: The SFX had the ability to morph into their surroundings by becoming echo-like when in enclosed spaces, making a more immersive experience and allowing the player to judge how far away opponent cars are and how fast they are travelling based upon the audio cues alone.
Split into simpler sentences: The SFX had the ability to morph into their surroundings by becoming echo-like when in enclosed spaces, making a more immersive experience. Even if you can't see cars behind you, you can sense where they are, how far away they are and how fast they are travelling based upon the audio cues alone.