If you are playing on an original PSP console (or PSP Go/Street), follow these steps:
Ensure the Save Data region matches your UMD or ISO region (e.g., a US save will not work on a European copy of the game). Backup First: save data need for speed underground rivals psp top
Use these search terms on trusted retro forums (like GBAtemp or CD Romance): If you are playing on an original PSP
The PSP version of "Underground Rivals" allowed for some multiplayer features, including Wi-Fi connections for racing against friends. While it may not have been as feature-rich as some of its console counterparts, it provided a unique experience for PSP owners. : Unlocks all Japanese and American tuner cars,
: Unlocks all Japanese and American tuner cars, including specific boss rewards like the Nissan Skyline R34 GTR (GT King) or the 1969 Dodge Charger (Tank).
Whether you are using an original PSP or the PPSSPP emulator, the process is similar.