There is no shortcutting this. The ECU, with its boost and map pressure sensors, is already effectively an electronic boost controller. If you had a way to trick the ECU you would be adding boost without the required fuel and timing map changes. This will very likely break your motor. The only safe way to add boost is to get the car properly tuned which will update all if the required maps in the ECU. While you can do this on stock hardware, it would make sense to also make any supporting hardware changes (especially exhaust and injectors) you are planning at the same time, so you don't have to pay for another tune later.