Multiple random cylinder misfire

A vq37vhr engine was brought to my attention after it was throwing a multiple random misfire code.

Here are the details:

1. Engine was just rebuilt after a porcelain spark plug shattered and bits of it fell down the combustion chamber.
2. The spark plug bits were retrieved and the engine was put back together.
3. A faulty angle wrench was used and may have thrown off the actual angle torque on the head bolts, along with a possibility of one bank to be only tightened to 95° instead of the full 190°.
4. Spark plugs on cylinder one and five (passenger side bank 1) are black and smell like burnt oil.
5. According to OBD readers car is running lean.
6. Milky white residue found at oil filler cap, even after wiping off and running engine again.
6. A bubble every three to four seconds seen coming from radiator filler cap. may be possible car was not bled all the way and radiator still releasing air but coolant level did not seem to go down as bubbles came up.
7. Leak down test was also performed while engine was cold.

Any suggestions on possible causes of the lean mixture and two black spark plugs?

Thank you