Help Brakes wont work properly no matter what i do.

[S142Fast]

So I'm trying to fix my brakes I have 300zx brake calipers on my S14 No Abs with stainless steel braided lines on all wheels I also have the gktech engine bay brake line delete kit I also upgraded my master cylinder to the 1 1/16. Everything I am about to explain has been bench bleed all lines have been bled and push rods on brake boosters have been adjusted to recommended specs of each master cylinder, and every time I bleed the brakes they all bleed good. With the car off the brake pedal feels hard but never locks to where you can't press it, when the car is on and vacuum is applied it gets extremely soft it always comes back up at each press but its way to soft where brakes feel like there not catching. I have tried 3 different brake booster 2 new master cylinders (stock) 7/8 master cylinder I have checked the check valves on the boosters and they seem to be working there's absolutely 0 leaks I have traced all the brake lines from wheel to master cylinder there's no leaks inside the cabin or at the master cylinders itself. Any help will be much appreciated.