[Brookshire my]

I have only had my ‘73 914 for a month and have not been happy with the brake
system’s stopping capabilities. Previous owner stated the system was “upgraded” to a BMW 3 series set up at the wheels. I bled the brake system today with new fluid. No bubbles and nothing in the system leaks. All pads are plenty thick and rotors mirror smooth. After the fluid replacement I feel no improvement. I am familiar with these systems working on my ‘64 356SC so no surprises here. The only option I can think of is a replacement master cylinder. The one there now matches pictures I have seen of the standard dual circuit for the 914. Maybe the internal parts are just worn. Any other ideas?
PS-Used DOT 4 fluid for the flush having no idea what was there previously.