Soft Pedal after Master Cylinder Change

Tundra owner going on 3 years. Love this truck. Has 245K miles on it, and still works amazing.

Noticed my brakes were getting soft, so decided to replace the master cylinder. Found out the hard way that just replacing the fluid would probably solved it but .. . .

I tried installing it, bled the lines on each wheel 20x, bled it inside the engine at the MC as well. Soft pedal. Also used a hand vacuum, put it at 25 lbs, overnight. Morning still was soft.

Had a mechanic friend redo everything with a new MC, bled the wheels, pumped it 8x each, bled again. Hooked computer up to check ABS, everything checks out. It does brake better now, but the pedal is still soft.

One thing he didn't do is use a power bleeder to pressurize it more, but his hoses were 'hosed'.

Any clues on what I'm missing?

 

Could be the booster?

my 07 got super spongy. Did brakes all around and MC. Read that it could be the booster too, but the new brakes and MC fixed it. The booster can leak from what I have read.

 

Took it to the shop. When I bled the rear brakes I used the bolt to bleed, which is not doable to keep the air out. They replaced the rusted nipples, rebled all the wheels, now operating correctly.