The Gravel Co team left behind the security of their day jobs to become rally drivers which meant transforming a 1995 Subaru Impreza from an underpowered EJ22T turbo four-cylinder into a 3.0L EZ30 naturally aspirated flat-six.

The original engine produced only around 80–90 wheel horsepower, making it difficult for the team to compete with faster rally cars. 

The team obtains an EZ30 engine from a crashed Subaru Tribeca, despite uncertainty about its condition. They install it under a tight deadline and make several modifications, including a new subframe, upgraded injectors, a baffled oil pan, lighter components, improved headers, a custom exhaust, and a 4.44 final-drive transmission. 

The installation requires significant fabrication, cooling work, and wiring. A Haltech Elite 2500 standalone ECU is fitted to manage the new engine. Eventually, the engine starts successfully and survives testing to 7,200 RPM. 

On the dyno, the engine produces approximately 180 wheel horsepower. The swap is completed only hours before the next rally, giving the team a much more powerful and exciting car.

However, the episode ends with a dramatic setback: within 48 hours, the car is destroyed and both the driver and co-driver are taken to hospital.