This guide is excellent. I would have been stuck at removing the logic board without it! Sure glad I bought the iFixit toolkit on Black Friday. What I installed was Ballistix Sport DDR4-2666 (2x16GB). But Mac reports it is running at 2400MHz, not 2666. Otherwise it is working great. Has anyone been able to correct RAM speeds? On a PC I’d fiddle with BIOS settings and kick in the XMP profile, but is there anything I can do on a Mac?