The wrong mc was on landy when I got it I think servo is type 80.NRC 9529 is the correct one.
Paddocks have a seal kit at just £6 ish.
Pop one in your old one and see if the brakes are better.
One clip, a good clean and pop it in.
Did you get the right servo if you got a new one.
Did you try each wheel for locking up with someone pushing the pedal as mentioned previously.
Is the servo pipe in the right place on the engine.