Basically 1K6 is for the GTI and R32 1K0 is normal diesel and petrol none 300kph/180mph models
You then have the middle numbers 920 which is the vw cat number 9 main segment electric system and 20 segment number for instrument clusters,
Then you have the 3 end numbers the first number is for mph(9) or kph( 8 ) the second number is for low(5) mid(6) or highline(7) and then the year 0(2004-2005) 1(2005) 2(2006) 3(2006-2007) 4( 2008-)
Lastly spec the letters on the end GTI early 2004-2005 EX up to late 2006 its DX after 2006 its X for, R32 its FX for early and BX for late models
So you would want for a GTI 1K6 - 920 - mph 9 highline 7 then 2006 either early 2 late 3 so 1K6 920 972 or 973 DX
Hope that helps?
Darren