i cant remember which way round it is but on one of the petrol engine managemnet courses i have done this question was brought up, on one of either the 180 or the 210 or 225 S3 or TT engines everything is the same except for the map in the ECU, this was to cut down costs and save money when making the different spec S lines!
i believe it was the 210 that could be just swopped and coded over to allow 225 performance, but i cannot be certain!
best just do as recommended above, get your ECU chipped or remapped and you will get more of a performance gain than that anyway, also for a start the dealer will charge you for swopping and coding new units approx 2hrs labour and if it does not work then you will be charged to have it put back then you will have to supply all ID!
cheaper and better get a REMAP approx £500