K is the lowest needed not L, though not all Ks are suitable.
Its likely yours will already have a K
Youll need to scan your CAN Gateway with VCDS and post up the SW and HW revisions of it.
Mine had a K and it was absolutely fine.
Mine is the following - same as SteveP
Address 19: CAN Gateway        Labels: 1K0-907-530.lbl
   Part No SW: 1K0 907 530 K    HW: 1K0 907 951 
   Component: J533__Gateway   H04 0020  
   Revision:   H04 02    Serial number: 281106F1001231
   Coding: 3F0F034007000001
   Shop #: WSC 01287 785 00200
   VCID: 2F671974C78D