I hope there good drugs, but I don't believe the w is for wagon and k for ute, but I have been known 2 be wrong on many occasions *L*
Both letters from what i can see on Nissan Fast are just color codes, not sure what the difference in greys are though.
If you have problems with Nissan Fast just PM me, I might be able 2 help out.
There is a thread on here that I done a while back might help you with the install if you have troubles.
http://www.nissanpatrol.com.au/forum...tware-Download
Cheers,
Todd