I had been having a problem with my Firebird brakes. The pedal was hard but the stopping power was just not there.
Could not lock any of the brakes from any speed and I really had to stomp with force on the pedal.....like both feet pushing as hard as possible. It had been getting progressively worse over time. It wasn't until I got the other Firebird that in comparison the differences were obvious.
It first started 5 years ago....ya 5 years and it'* taken this long to finally solve it!

The Brake specialist shop said it was the first time they had been stumped in 30 years.

So the first logical choice since the actual brakes/rotors were new, was to replace the master cylinder.
No change.
Drove for some time then replaced the Power Booster.
No change.
Drove for some time then replaced the pads, shoes and Proportioning valve.
No change.
Drove for some time then replaced all the hoses.
No change.
By this time 3 years had passed since replacing the Power Booster.
The Brake shop that did the Booster originally did all the work. They replaced the Booster again and voila! I have stopping power again! Yeah!!!!!
....and they only charged me $165. for everything.

The 4 wDiscs on the T/A are better. Much less tendency to lock up the rears.
The Bonneville has 4 wDiscs also.
I replaced all the calipers with rebuild units on the T/A. The rebuild rear disc calipers were $165 ea. with trade in.

I wish I had ticked the option box when I ordered my Formula but it'* not too bad, a lot cheap to maintain and now with all new components it'* clean and fresh.