Once again, this has already been explained. The previous GT350 was put on a dyno outside of the environment at World Motorsports. The 2019 was put in this new environment where they make more power, as the owners of the dyno explain.
You're not imagining anything. There's a lot of difference between a 16 non-R and a 19R. Should feel faster, quicker and lighter on its feet because it is. The 19 Non-R's have improved with the cup2's and recal suspension but the R is still the King.
IIRC @honeybadger's heads didn't get ported, just rebuilt with more robust parts to handle the sustained high RPM. Same thing with the bottom end. His 545 RWHP was with a cat-less non-factory exhaust and a non-factory tune running E85. It doesn't surprise me that it compares favorably to the car in the dyno test reported by the OP, which was a stock 2019.
I plan to in the next couple of weeks, as soon as I get past 1000 miles. I'm at about 900 at this point. I've already called the local mustang performance shop and discussed prices and options.
Whatever would be most relevant to compare the factory 526 HP rating.
