ive got a 2lt zetec focus mk1 that needs an engine ive found a cheap 1.8 zetec engine i no these engines look identical but what would i have to change i was thinking just the ecu or is the loom diffrent aswell.

 

The MK1 Focus ZETEC-E 1.8/2.0 looms are the same so you have no worries there - they also both use the EEC-V 60-Pin ECU but you're right in saying that you may need the 1.8 ECU for it to run properly although I would try it on the 2.0 first, I reckon it would run on that to be honest.