I'm not sure about this, but from what I could understand from the GST thread, is that the car's on-board boost controller has a maximum value that cannot be changed. So what the boost pill does, is restricts the amount of boost going to the sensor, fooling it to be at a slightly lower value. The ECU now keeps the wastegate shut for a longer period of time, allowing more boost to build, and more power to be generated. That said, it MUST be reflashed to have proper AFR when the boost is increased!

I'm not sure how aftermarket boost controllers work, especially in conjunction with the one in the car, so I cannot say if they allow more boost to be held, or if they can just allow a reduction in pressure from maximum.

 

The boost pill is designed specifically to be used with basemaps that are already tuned to use the pill. A boost controller will have the same end result, except you'd need to have your ecu tuned for the boost target you've set. The boost pill's major advantage is that it is specifically designed to bring the Ralliart's stock turbo to its maximum safe boost level.