Sorry a little behind on getting to this reply! Waldig at 1.9 Bar (1.0 Bar = accepted by Europe as approximately an atmosphere of pressure) you would be pushing almost 28 lbs boost at STP. That's impressive! But considering the issues with intake charge heat and knock (at that kind of boost) could your power issues have to do with ignition pull back by the ecu, due to knock detection? Having maintained several WWII era super charged aircraft, boost and consequental knock turned high performance engines into steel and aluminum scrap. Especially when pushing the envelope down on the deck, i.e. pylon racing. I am curious as to what you find!