16v conversion won’t start

[Henry1998]

Hello there people I have a 1.1 2000 reg saxo and have recently put a 1600 j4 gti engine in it they both had 3 plug ecu and the chassis plug was the same size although some off the pins aren’t in the right place,however all the pins that could start the car match up and with my ecu being unlocked yesterday I’m completely baffled anyhelp would be greatly appreciated