I dont pretend to know all the wiring variations but here is an earlier one,
Notice how terminal 3 of the start relay is always alive fed from fuse C[You must be registered and logged in to see this link.]
Anyway if you remove the relay and probe the socket terminal 3 you will find it alive.
I have never looked to see what size wire is feeding terminal 3 but I doubt its any significant size.
I do know that on my 2007 the wire from terminal 5 back to the starter solenoid was really wimpy, I replaced that with an 18 AWG and the solenoid operated 3 x as fast.
Next look at this 2008 diagram, the Start relay is now fed from a yellow wire that in turn is fed from Fuse 2 which is only alive when the key is ON[You must be registered and logged in to see this link.]
Also now you have a second Start relay. The additional wiring up through the ignition switch and back through another fuse then to the relay makes the circuit weak (not able to deliver much current) hence I call it the weak yellow wire.
So the key to finding out how your bike is wired is to unplug the start relay and find out if terminal 3 is alive with the key OFF.
The factory seem to be oblivious of the fact that the starter solenoid will draw 50 Amps or more for a split second if its wired right, it needs that huge rush of current to move from rest and engage the gear, once its engaged the current drops right back to around 10 Amps.
There are two coils inside the solenoid (Guzzi only show 1)
The Grunt coil that draws 40 Amps and does most of the hard work.
The Holding coil that only has to hold the solenoid in place while cranking and draws around 10 Amps.
The combination of these two coils probably starts off at around 30 Amps and goes downhill from there as the bike ages.
With a direct feed to the relay it will draw more like the 50 Amps the starter was designed for.
If you already have a direct feed to the relay e.g. pre 2007 don't waste your money on a kit just upgrade the wires to and fro.
For the bikes with wiring through the ignition switch re-wire the feed direct with a 20 Amp fuse and upgrade the wire from relay to solenoid.
I really don't know why they added a second start relay but it does bypass all the ECU interlocks, I suspect they might have found the starter was dropping out due to low Voltage while cranking, i'm sure a direct feed would have solved that, the 2007 only had 1 relay.
If you have a meter and you are curious measure the resistance from the solenoid Spade terminal to chassis then calculate by Ohm's law how much current it will draw at 12 Volts