Either you like it or not most of the pre-revision cars were reading lower than the 170whp number you mentioned. Dyno type and specific calibration can make a difference, but these low readings were quite common especially on early '12 production cars. This is not the same with the revised cars. All these have been discussed in detail more than a year ago and were admitted by people that worked actually in the project.
"Upgraded engine, catalog about 5 horsepower more. Realistic more like 15 to 20 because it's actually... the real horsepower is actually closer to the catalog horsepower now"