One thing I'd try first would be getting a used IAW16 car unit out of a FIAT, Lancia or similar. Ebay sometimes has them quite cheap. It might sound risky, nevertheless I'd try it out in the bike, how the pump acts etc. the bike might start even. Third step then would be to switch the eeproms. Should this scenario fail you have at least some spareparts someone could use to repair your's (the big Vishay diode for instance and others).
hubert
Edit: used Guzzi parts, working, are offered for about 200 Euros. Probably the better way to go.