The purpose of the actuator is to allow you to hold boost alot better than the stock actuator. It usually is set at 11psi(I believe)out of the packet but can be adjusted via screw to increase boost. Doesnt do too much on the stock t25 from what I've heard due to the characteristics that turbo but will do wonders on any aftermarket turbo. You might see a little bit better hold on boost on the t25 but Im not sure.