I notice you're asking about a "Forza Motorsport 4 PSP ISO" — however, . It was an Xbox 360 exclusive developed by Turn 10 Studios and published by Microsoft in 2011.
Why would someone claim an "exclusive" PSP version of an Xbox 360 game? In 2011, Sony and Microsoft were locked in a bitter console war. A rumor circulated on PSP-Hacks.com that Microsoft secretly allowed a PSP port of Forza 4 to test mobile cloud streaming. This was false. However, the term "exclusive" was added to ISO titles to imply that this was a leaked from a Microsoft employee’s laptop—a "PSP-exclusive" beta. forza motorsport 4 psp iso exclusive
If you want a similar realistic racing experience on the PSP, the official Gran Turismo (PSP) is the closest legitimate simulation title available for that handheld. I notice you're asking about a "Forza Motorsport
I think there may be some confusion here! In 2011, Sony and Microsoft were locked in