Whats the difference between the 2001 VW passat and the 2001.5 passat?

I'm looking at buying a used one, and how can I tell the difference?Whats the difference between the 2001 VW passat and the 2001.5 passat?different MAF, instrument cluster, chrome trim, ecu mapping, thats about it, oh and the tail-lights.

d3100