according to their documentation, it plugs into both the MAP, TIP and PPS sensors, compares the readings between MAP and TIP (PPS activates) and adjusts them to manage boost calculations.
in the end, these boost "foolers" all generally work the same, they knock the readings down to fool the computer into holding the wastegate closed longer to allow higher boost. how well they manage it depending on throttle and rpm is what can set them apart. i think the JMS one you can turn up and down to give your more or less boost.
