Windows 8.1 FPS drawdowns (Grand Theft Auto: Vice City)

Greetings who is the asset, the problem with the FPS is the latest version of the driver, the FPS drawdown is up to 15, usually due to a blow to other cars, but it sometimes sags just like that, when you ride a motorcycle, the FPS fell as if due to the loading of the cars. Who knows what the problem is?