Reach the indicated rank to unlock the corresponding performance upgrade:

Level 1 Performance upgrades for Group 1 vehicles: Get the "Navigator" rank 
(800 Reputation). 
Level 1 Performance upgrades for Group 2 vehicles: Get the "Driver" rank 
(5,600 Reputation). 
Level 1 Performance upgrades for Group 3 vehicles: Get the "Elite Racer" rank 
(13,700 Reputation). 
Level 1 Performance upgrades for Group 4 vehicles: Get the "Savant" rank 
(22,760 Reputation). 
Level 2 Performance upgrades for Group 1 vehicles: Get the "Rookie" rank 
(3,610 Reputation). 
Level 2 Performance upgrades for Group 2 vehicles: Get the "Veteran" rank 
(10,760 Reputation). 
Level 2 Performance upgrades for Group 3 vehicles: Get the "Legend" rank 
(19,540 Reputation). 
Level 2 Performance upgrades for Group 4 vehicles: Get the "Hero" rank (26,160 
Reputation).