Wanted

Gti engine with inlet manifold and sensors! My gti has recently failed it's mot due to high emissions of 10.3!! Someone please help

Dont think you need another engine just because of emissions 
Is it a ph1 or 2 car?
If youv got a cat then its your right to warm it up properly if it fails at first

They tried it warm on second attempt and it made no difference

Well then check all of the breather pipes, o2 sensor, filter etc
Some ph1 gti 89-92 had a small knob on the inner fuse panel that changed the richness 
What mods have you done?
If its just a chip and not much else then that could be it