Well, here's the comparison.
They are different, but physically the same size. Note how the earlier one appears to have a larger cat on it, perhaps that's value engineering....
Anyway, as you can see both lambda sensors are off the Aero pipe. The 2.0 one has the rear one still in situ, and to be honest the only way that is coming off is with a grinder, so for now I will leave the old one on
In other news after many hours of using a dremmel, then needle files, then a small round file I got to the point where the threads were just becoming visible. I gave it a final flurry and the hole seemed ready for a tap to be run down it. Which is when I realised that the final flurry was far more efficient in terms of removing metal (because I suppose I had got to the cast iron, instead of the steel), which meant it wasn't really possible to retap the hole. So, time to drill it out & helicoil.
Tapping cast iron seems quite a bit more challenging than steel. It has hard bits and soft bits, seems quite capable of breaking the tap if used incorrectly, but I'm trying not to exert too much force & using oil to lubricate. The tap is just through the hole, but it's not fully threaded to the bottom yet
Still, the turbo has zero play, so it's worth saving