Given it uses memory injection, you probably have to disable any antivirus or add an exception for the exe, such that it can modify another programs' memory addresses (antivirus programs block this) - also running as administrator is likely to be required.
I suspect the reason your machine lags while running it is in fact that some other process is attempting to block sapt's activity.
Naturally, on other machines, the effect of the program is to indeed
improve the performance of san andreas, not reduce it's speed.