BD - I came across the same thing as I have an 08, which is the newer Givi model code (PL362 2007+) as opposed to the earlier model code of (PL353 2004-06).

PL353 always came out cheaper in my searches.

The only differences between the years that I could see on the bikes were very slightly different passenger grab rails and slightly different footpeg hanger that is noticeable with black, rounded tubing on the 2006 hanger as opposed to square, raw alloy tubing on the later models. I state these two items as they are critical for the fitment of the pannier rails.

Clearly, for you, looking at the passenger grab rails is not helpful..... but the footpeg hanger may be a clue?

As an aside, the same Yamaha rear rack is listed as fitting all years.

Pictures of both:
http://www.asl-testsite.co.uk/motors...T660R-2004.jpg
http://www.arpem.com/motos/modelos/y...-660-r-ld1.jpg

I'm not sure if this is helpful.... or me simply increasing my post-count Simply passing on my observations that I have picked up in my research. Again, hopefully someone with some real world experience will come along and help us out!