Replaced Rear Brakes/Rotors on 2014 SR5 - constant squeaking!

I got a set of Powerstop OEM Daily Driver pads and rotors for the rear brakes on my 4Runner (@68k miles). Brake pad wear on the original pads was even.
I followed their instructions for installation and break-in, but am still getting a constant squeaking noise from both sides.

I performed the following checks:

• pulled the brakes back off
• re-lubed the pins and backs of the pads
• pushed the caliper piston fully back into the caliper
• checked for debris in the caliper
• cleaned the rotor
• checked/cleaned the parking brake shoes and inside shoe surface of the rotor

The squeaking noise is still there, when driving at any speed, maybe a bit less when braking.

I have heard it is harder to break in the rear pads, since more of the braking is done in the front, but wonder what else I should check/fix to stop the noise.