There is a seller on eBay selling a universal wiring harness click here I have looked at the models they think it will fit and I am concerned as the models are so very different, some with ECU and some not. Also they claim to fit all European and Japanese manufacturers models!
The plugs supplied do not look right for a Guzzi and the wire colours are random.
Beware if you go down this route as I think these will not fit your bike! 
I just received this from the seller (CAPITALS are their own, I applied the italics)
hELLO THERE,
we MENTION THE FOLLIWING IN THE ADVERT TEXT:
N.B. The compatibility list and any motorcycle makes / models that you see in the advert text are just a loose guide; this is a wiring loom designed for anyone with excellent electrical knowledge and advanced home mechanics. If you need a loom, but aren’t confident enough to fit this, please take it to a professional workshop.
I would not recommend these to a Guzzi owner.
Best wishes Chris
Complete waste of money. Won’t actually ‘FIT’ anything!