Prior to this post, I forgot to mention that the ignition box was dismantled and replaced with a new one. This was just to see if it did the performance any better. It did not, so the ignition box was ruled out as a factor.
The 260 is currently being assembled, i.e. fitting in the oil pump, and new brake pads, before it will be put on the road for the final test run. And hopefully, it will run well.
126 tailed by a 203, 129 leading the pack.