As far as i know unless you give the navara more fuel extra boost does nothing, iv'e had a manual boost controller on mine and made no difference what so ever!
yes it upped the boost to 22 psi according to the gauge but made no difference in performance or power, but because of the ECU controlling boost levels it made no difference! cause the ECU won't allow more fuel and they are not adjustable
Now in saying that i have added a unichip to mine which has made a hell of a difference, but still to get more boost the chip has to be adjusted and more fuel given.