Superior Millenium Cylinders not shipping

The IO-520 out of our Cessna 210 is being overhauled by Custom
Airmotive in Tulsa. We had wanted to go with new Millenium cylinders,
but Superior has a halt on shipping them. A Superior rep said there
were some minor design changes that the FAA is requiring them to run-
test to assure life to TBO. They have not been shipping any of these
cylinders for 60 days or so, and said that the testing would likely
require another 45 days, resulting in shipments resuming in late
January.

I have seen that Millenium vs. ECI vs. Factory (Continental in my
case) has been a perennial topic here but not lately. My current
decision basically boils down to "wait for the Milleniums" vs. go with
ECI. Does anyone have recent experience or recent information about
quality, reliability, etc, between those options, or other options or
thoughts?

Thanks,
John Clonts
Temple, Texas