think of the newest polo gti (130bhp), mk4 golf gti (150 then 180bhp with the anni) and mk1 audi tt 1.8 (220bhp). all have the same 1.8T engine (also found in leon/ibiza cupras too etc), but different maps.
That is complete bollox. The 225 has completely different, revised internals compared to the 180 in the 1.8 20VT. The 2 litre FSI turbo also comes with completely different "hardware", dependent on the standard state of tune.
The golf and TT both share AUM and AUQ engines... (there's others they don't share though)
You still havn't grasped the nettle fully!
a remap is pretty much undectable - little to no chance of this getting flagged up and voiding your warranty,
Hmm, a remap may be undectectable, on the 'puter - but any experienced stealer techhy will know something is "different" on a test drive! 
any techy who admitted to finding something different like that would have to admit to thrashing the sh!t off your car too tho! it's also a decent point but then how would they prove it? no exactly gonna RR your car are they...
Again, more bollox. You don't need to "thrash" a car on a test drive. Simple part throttle acceleration tests will reveal differences in torque production (which would then indicate differences in potential power, higher up the rev range).
If they did have valid suspicions, then they simply download the ECU map on a data stick, and send it back to VW Germany for a detailed analysis - and I strongly guess that VW would know their own maps!
