Breaks Anyone?

Anyone?
2007 Tundra 5.7 SR5 4WD 265,000 miles
there is a squeal coming from the driver front side that i have been working with and trying to resolve for a couple years and a few thousand miles.
I thought the squeal was the obvious brakes squeal, but it is not.
I have replaced the front calipers, rotors, and pads. That did not resolve the noise. i have switched drivers side to passenger side in different configurations, I have bleed the system multiple times, I have replaced everything that rotates or comes in contact with a part that rotates.
Each time I have replaced parts, it has been a very temporary silence that only lasts for potentially a day or so, maybe after the brake has been applied after 8-10 times. Sometimes even as I am backing out of the garage I find it never left.

I have figured out that the noise is not directional or a rotation squeal. It only happens at very low speeds, lets say under 5 MPH.
like at a stop light, or going through a drive through, or moving through traffic at low speed with constant pressure on the brake pedal, or even backing a boat into the water at a ramp.
It only happens mid pedal, not light pedal and it always stops at heavy pedal when you near a complete stop. The squeal is always a consistent pitch and never changes with the rotation of the wheels. It doesn't not matter if it is forward or reverse, the squeal is the same.

This is a pressure related issue (In my Opinion)
Has anyone ever heard of this issue?
Any Ideas?

 

Have you replaced the backing plates ? Did you use Sil-glyde on the plates ? Pins? caliper pad ears ?

 

backing plates 3 times, pins and springs 3 times, calipers are new, pads are new, rotors are new. and i always use a anti-seize or lubricant on everything that has friction other than the rotors and pads of course.