Ich hoffe, ich kann damit etwas helfen. 
  
All the following turbos have the same installation dimensions and
 thermodynamical performance. The differences are only in the actuator that
 opens the turbine bypass valve:
 K03-011 (5303 988 0011) 150 hp, 65 N actuator
 K03-026 180 hp, 85 N actuator
 K03-035 180 hp, 85 N actuator
 K03-044 150 hp, 65 N actuator
 K03-045 156 hp (Ibiza Cupra), 85 N actuator with 2 ports
 K03-049 150 hp (Sharan/Alhambra), 65 N actuator
 The 180 hp versions have an actuator with a higher opening force due to the
 higher exhaust gas pressure (which is a consequence of the higher boost
 pressure). Otherwise the valve would be pushed open by the exhaust gas
 pressure. 
 The following turbos are a further development (since 2000) and have an
 improved and slightly larger compressor while using the same turbine (still
 with the same installation dimensions):
 K03-052 180 hp, 85 N actuator
 K03-053 150 hp, 85 N actuator
 K03-058 150 hp/180 hp, 85 N actuator 
 Consequentially, putting a 180 hp turbo on a 150 hp engine will not bring
 about any change in performance, but putting on a K03-052/053/058 instead of
 the older versions will bring a slight improvement in engine efficiency.
 Additionally, with re-mapping the ECU you can achieve about 215 hp without
 danger of overspeeding the turbo. With the older turbos, 195 hp is the
 limit.