2007 brakes

[barneskite]

Hi, new to the forum and i cant read all the resources so....
I have a caddy that i have just put a replacement engine in, and WITH the engine running the brake pedal is slow to release resulting in dragging brakes... but without the engine running returns as normal... Servo problem? Master cylinder?
I have vacuum as the pedal sinks normally when starting the engine, its like the pedal has not enough power to return when it has vacuum from the engine..

Any ideas?
TIA
Tim

[STP]

I'd be wondering about the return spring on the pedal, is it missing or broken. That might explain the behaviour. If you flick the pedal up with your foot does it go back to normal and stay up? I've had the issue before due to a sticking caliper too, golfs used to be terrible for it.