What does VW do to improve HP and Torque from their 1.4 TSI engine?
CAXA: 90 KW @ 5000 200 NM @ 1500-4000
CAVD 118 KW @ 5800 240 NM @ 1500-4500
Both engines you mentioned have a supercharger and turbo combination. The performance difference is achieved by increasing the boost pressure to the engine. While this might be done only by using different ECU maps for small performance differences, the big performance differences usually require higher capacity parts as well, especially for the turbos, injectors and cooling.
A short google search revealed the following for these engines:
Not to forget different fuel specs:
The differing specs of VW engines are (I believe) mainly done by varying the ECU maps - Which is why a lot of power can be gained from the lower-spec engines by chipping them up to (and beyond) the higher-spec versions.