Well I've been able to drive it a little. First was around the farm and then on the road.
Around the farm it seems to go well. I don't travel very far or fast so the real test in on the road.
These drives are spread out over days and in some cases weeks. I don't always have time available!
DRIVE 1
I headed out the gate and got about 50 metres! Limp Mode. Software was complaining about the accelerator. It is electronic and has two circuits.
I redid the wiring, making sure all the joins were OK.
Accelerator seemed too be fixed.
DRIVE 2
80Km drive to my house and back. It was a rather embarrassing drive as the TDI belched black smoke. So much so that if there was a car behind me, it wasn't visible !!!!
Problem was a split in the intercooler pipe.
Intercooler pipe fixed. Went for a 16kms drive. Fantastic. No smoke

I drove to my shed and stopped the G60. Loaded tools and planned to take it home (40Kms). I jumped in to start it, But it was a no start.
After 4 days of trying everything I knew I reached out to a TDI Forum. I reported my symptoms and some guy said he had a similar experience and his cause was out of fuel. I had at least 40 litres of fuel but decided to run a tube from a jerry can to the electric fuel pump. 5 minutes later it was going. So not sure what was the real cause but I was out of time and I'll return in a few days to continue the testing.
In chasing down this error the software reported two other errors - but neither of these should have stopped it starting.
Error 1. Complaining about the accelerator again. So I need to get a new accelerator pedal. I find this hard to believe as it worked on the Jetta.
Error 2. Crankshaft sensor faulty. The TDI has both a crankshaft sensor and camshaft sensor. This model TDI will still run if either are faulty but limits RPM to about 3000. To sort out this error I may need to pull the engine out to get to the sensor - I don't kook forward to that. I did put in a new sensor before I installed the TDI in the G60, so I'm hoping it is the wiring - but that is still difficult to get at.
DRIVE 3 -
Watch this space ....