Dodge Truck Brakes

I have struck out on searches and on other forums so I am looking for help from my peeps.

2006 Mega Cab 1500 4x4

Issue:
Intermittent RED brake light and occasional slight Canary singing from 5-30MPH and slight pull to the left.

I have changed both front wheel hubs.
Changed both rotors, calipers, and pads.
Replaced the rear wheel speed sensor.
Rotated all of the tires more than once
Two alignments
Parking brake has no play
Fluid levels ok.

I have not changed the rear pads or rotors yet
Nor the rear parking brake shoes

What is left? vacuum to booster? brake control by pedal?

any help would be great.