Got the call from Nathan (Guzzi trained technician when Streffords acted as an authorized sales agent & repair shop) in Worcester to inform me that he’s replaced nearly every bit of “rubber pipe” on the fuel injection system and its running well with the inclusion of the new fuel pressure regulator, the problem appears resolved. However, he informed me it developed an oil leak during warming up for testing - the “rubber” pipe between the heads split, (there’s a theme developing here!) its now replaced. Anyone considering the older injection models does need to think about this aspect, with carburetors there just a bit of pipe from the tank to the carb float bowls to replace. There’s a lot more “rubber” on a Guzzi fuel injection system and the tiniest leak or split in any of the pipes whether for fuel or for air / vacuum, creates issues, its a nightmare to trace the fault as I have found.
As a materials engineer I know rubber has a finite life and 25-30 years seem to be the limit - with the addition of E10 fuel we can expect life to fall even further, I am going to explore fuel additions to help preserve the system, If you think about it, you have a lot of time when fuel is just sitting in the pipes, pump, filter and regulator just rotting the system - say on a winter lay up.
Any members with any thoughts on this specific subject?
Are there any “brews” to be added to the tank that can help preserve the system?
On a final note, the electronics are standing up to age, the ECU, sensors and relays appear ok. Will run it for a bit and see how we fare.
Thanks for all your contributions and suggestionsfor parts etc in the thread, it’s what a good forum is for 
found this and its not expensive - if it works on lawn mowers for winter lay ups its worth exploring…anyone have any experience?
Very useful information Paul, I hope that has cured your Cali of issues.
As for fuel additives and suchlike, there is a fuel called Aspen, 4 stroke and also a 2-stroke premix, however it retails at around £25/5L…
The other option is either Shell V Power or (of all things) Tesco Momentum. Both are marked as E5, however they are both 99 octane and ethanol free. Obviously they are more expensive than standard E10, however it’s an option for laying up over winter or whatever.
Cheers!
Jeff
Thanks Jeff, Picked up the bike Friday PM after work, more to this story now, as well as the fuel pressure regulator, the TPS had to be replaced, (as Mike Rdec had suggested, this component could have been faulty) when they road tested the bike, they found it to surge and still run erratically, after testing the output from the TPS, they determined it was indeed “faulty” so stuck on a new one, £71.00 later and all is well. Finally, they never told me they had partially drained the tank to facilitate working on the bike and I ran out of fuel a few miles up the road! A borrowed litre of petrol from a friendly car dealer got me to a petrol station,a full tank of super unleaded and its all crisp and running nicely (~60 miles on the clock now) Looking on the bright side,at least I know there’s no more crudy petrol in the system and the low fuel sensor in the tank is kaput! Old bikes = never ending story - but any other followers of this issue looking for a cure would be well advised to look at the TPS initially and work back from there. I was unfortunate to have the double whammy of a FP regulator and TPS failing at a similar time. In all, 90% of the original fuel system is now new - fuel filter and pump have also been changed plus most of the petrol pipes.