I call BS.
You've set yourself up as the "authority" in an "appeal to authority" logical fallacy.
The fact that you "think" there are huge variances, simply does not make it true.
Yes, for sure there are both engineering and quality assurance tolerances, but these things are not carved out by hand. Modern manufacturing tracks part variance during manufacture and intake and even fastener torque for everything on the assembly line.
As for backing new vehicles of the trailer.... one of them was first to come off, and had more time to fully warm up. The other had not, making the engine cooler than the first one... BAM... differing performance. (this same trick is used by a lot of "performance enhancing" products to "prove" dyno gains.
Unless you've Dynoed a statistically significant number of identical builds, it's just you convincing yourself there's a huge gap.
I mean, I guess it's a good introductory post to a new automotive forum... it gets lots of attention and reactions but I wouldn't count it as the Gospel.
But... welcome to the group. Lots of awesome folks sharing tips, tricks, experiences, deals, and a love for Jeeps with huge V8s.