HI guys have replaced engine on an A4 1999 - fitted engine from 2000 A6. (2.5 diesel)

Initially was not getting ECU coms on diagnostics so - bought a A6 ECU and fitted it after doing Immo off.

but still at same issue - no power at fuel pump connection relay tested to be ok.
when I try to jump the relay port with thin pins the pins instantly get red hot even though the fuel pump connector is disconnected, does the fuel pump relay controll something else swell? maybe glow plugs? is the relay for this vehicle 372 or something else?
Another thing that's been noticed is when cranking engine there is no activity at the fuel pump however as soon as I STOP cranking the fuel pump makes a sound for a brief second.
Currently NO DTC in car so I am lost what the issue could be any advice or pointers would be greatly appreciates.