Any file claiming to be an official "Forza PSP ISO" is likely one of the following:
If you want a high-quality racing experience on your PSP (or via the PPSSPP emulator), here is a blog post guide to the best legitimate alternatives that feel just like Forza. Forza PSP ISO: Myth vs. Reality forza psp iso
The legal way: rip your own UMDs using a hacked PSP or PS3. However, due to scarcity, many users download clean “redump” verified ISOs from archival databases (like the Internet Archive). We do not endorse piracy, but we acknowledge that abandonware preservation exists. Any file claiming to be an official "Forza
There is no official game for the PlayStation Portable (PSP) Go to product viewer dialog for this item. due to scarcity