Yeah the motor is VERY well engineered-I’m glad they didn’t put it in the IX like they originally planned and took the time to sort everything out. The new hybrid turbocharger and amazingly effecient factory o2 housing and downpipe make a world of difference also. Only car I know of that doesn’t really ‘gain’ power by going to a full turboback (catted) vs the factory setup. Only ‘major’ restriction seems to be the stock muffler (and cats of course).
See link here for info: http://perrinperformance.com/pages/show/80
HP/TQ Gains of Cat-Back vs Turbo-Back: http://perrinperformance.com/products/show/685/Cat-Back-Exhaust-Stealth-Black?category=6&model=26