PCSX2 settings? Plugin settings?
If you have many speedhacks enabled try without them or just find if any gives you fake FPS trouble, EE cyclerate/vu cycle stealing for example.
Core i5 3570k -- Geforce GTX 670 -- Windows 7 x64
I'm pretty sure he's getting inaccurate FPS due to VU cycle stealing. He should disable it. I also have Budokai 3 and Infinite World, and find that enabling VU cycle stealing at moderate results in slow mo gameplay for both, despite the counter showing 60fps. Without VU cycle stealing, I can run the games at fullspeed (around 68-70 fps without frame limit).
In fact, even setting VU cycle stealing to mild makes me lose around 5 fps. The game is probably dependent on the EE that starving it thru vu cycle stealing makes the game run much slower than intended, even though the frames are being pumped out at 60 fps.
+ geforce GT 440 @ Win7 64bit