mk5 gti

has anyone put a mk5 gti engine into a mk1.....

Its FSI, in other words, stratified fuel injection. If you don't know what this means, it means that the fuel is directly injected into the compressed air charge in the cylinder and burns much more quickly and in a different manner (heterogeneous, due to exact amount of fuel injected for required torque but excess air through electronic control of the mode and throttle opening). This is done for reasons of efficiency, having an engine sized for max power/torque then throttling it for part-load operation is less efficient than heterogeneous burning (compare regular petrol and diesel).

So, the fuel injectors are very different are are electrically 'driven' in a completely different way, also the ECU would need to know which mode to run the engine in (part load = heterogeneous but timed cycling to homogeneous, warm up mode, acceleration mode, high power mode, etc).

So far only one company has developed a standalone ECU capable of this and they have built a prototype and done an engine conversion. Its an R36 engine in a Mk2 Golf.

Maybe someone's done a conversion and adapted the stock ECU, on a 2.0 TFSI? IDK

+ its a very tall engine .

don`t forget to use correct fuel,stratification on works with high octane fuel 98 RON.
VW sales person usully forget to tell this when buy a new car because running costs are higher