First off cool story bro and if you can come up with a suggestion without pulling the head off speak now or forever shut up.
I didn't come to the conclusion a tuner/ builder and another highly recognized tuner (obvious reasons I'm not mentioning business names or tuners) came to the conclusion and with a problem that shows no obvious signs of what can be the problem, and every test to try and find the problem without taking the head off, my guess is your answer if this problem was presented to you is "it's fckd mate".
The reason for the tests is because if you have any idea (which you don't) is not to void warranty/ liability with the business that built the motor (and yes it was sent back to the original builder).
As for being out of business for a returned service/ product "end of story" every business in Australia...wait...the world would be out of business by your belief, and your "thinking" I'm shocked that you can put one foot in front of another each morning.
A number of reasons can pull different results, changing weather, cold/ hot, different gauges...etc.....far out I just realized why am I arguing with an idiot no one will know the difference .