This is very embarrasing for Lenovo! I see what you mean by the proprietary 14-pin connector (it has others upset as well
), and I cannot find a pinout published anywhere for this. One can probably be deduced from the wire colors along with maybe some voltmeter testing. If you have any detailed close-up photos of the connector that would be helpful.
If the pinout is a subset of the ATX standard 20 or 24-pin connectors then a standard one could be used by either cutting the connector down or inserting the pins into the shell from the original Lenovo PSU.
Note that the two 4-pin "SATA" power connectors appear to be outputs. I believe Lenovo would use additional cables from those connectors to one or two optional drives. Scott.