Hi I have some experiment, with your Miami court:
q9400, @stock clock in both cases (I baked a MoBo some ago, so I better not touch it anymore....

)
gtx280 @stock clock: fps drops down often below 40fps, lags, and slowdowns, nearly unplayable
gtx280 @OC10%: fps remains at the vsync value, 60 fps almost everytime, smal drops to 59,2 (negligible)
Sounds to me it has GPU limitations..... but the level of oc is not so much, but was enough for me for the smooth gameplay.
I did not want to switch off vsync, 'cause the picture is tearing on my TV....
ENB on
Everything is set on max, res: 1366x768
This mod is awesome, btw, it was worth OC-ing a little bit for it....
