boost control is handled with spring pressure. A potential downside with pure tuner style is a slower initial ramp up due to the actuator opening gradually before it is time which bleeds off some of the intial spool up. This is the reason the granger style manual controllers became popular...no boost reaches the actuator until just before the opening point....this emulates the chip control technique of holding the solenoid open initially before reverting to duty cycle control
If one has a bit too much converter for the tires, then pure tuner style can sometimes soften the initial hit.
