Does Power Cord Require Burn-In To Sound Good?

There is a difference between the same "specs" and measuring the same under a range of test conditions. If they measure the same under a variety of test conditions then it will be hard to tell them apart  (just like what happens in blind testing, where people have a hard time telling differences if they are able to at all).  Tubes rarely measure the same so there goes that out the window. Wire inside the amp ... you will never be able to detect that change unless we are talking shielded/no shielded for a low level signal cable or an undersized higher current carrying conductor. Good grounding actually shows up in detailed measurements.

audio2design

... you will never be able to detect that change unless we are talking shielded/no shielded for a low level signal cable ...

In the words of attdavid, robertcan, roberttdid and probably other of your usernames  who have since been blocked from A'gon, and in words you've posted under your current user name:

Facts submitted without evidence can be dismissed without evidence.

I love this BS...
Just take that "recommended" power cable, and use it with your castle.
By the time your tea will taste better, it will also sound better.
The only thing that needs BI are mechanical or electromechanical components.
Copper conductors? Need no BI. it's a dull statement of a saler to make you keep a product that made no difference at all and he really wants to keep the sale rather than reofun you.
One of the best froud inventions of the Audio market.