Select arcade mode, then highlight the "Hard" selection on the difficulty selection screen. Hold L1 + R1 until it changes to "Professional".
Toyota Sprinter Truendo GT-Apex:
Successfully complete the Sunday Cup with gold medals in all three races to unlock the Toyota Sprinter Truendo GT-Apex.
Mazda Eunos Roadster:
Successfully complete the Cupman Cup with gold medals in all three races to unlock the Mazda Eunos Roadster.
Mazda Roadster RS:
Successfully complete the Spider and Roadster cups with gold medals in all races to unlock the Mazda Roadster RS.
Nissan Silvia K's 1800cc:
Win the Beginner FR Challenge series to unlock the Nissan Silvia K's 1800cc.
Silver Honda CRX Del Sol SiR:
Win the Beginner Race of NA Sports series to unlock Silver Honda CRX Del Sol SiR.
Successfully complete each tier of tracks in arcade mode on any difficulty setting to unlock the next tier of tracks:
Super Speedway, Midfield Raceway, Smokey Mountain, Swiss Alps, Trial Mountain, Midfield Raceway II.
Smokey Mountain II, Tokyo R246, Grand Valley Speedway, Laguna Seca Raceway, Rome Circuit, Tahiti Circuit.
Swiss Alps II, Trial Mountain II, Deep Forest Raceway II, Special Stage Route 5, Seattle Circuit, Test Course.
Added by: Team SuperCheats , ID#1463