The pistons are new so yes they are pit free, the caliper bores seem good, I have also used 600 grit wet and dry to smooth them off and try and remove and pits. It appears the issue is the same or more or less the same on both sides. The culprit is, I suspect, that when I had the calipers powder coated the idiot that did the job did BOTH sides of the calipers so I got them back and had to spend hours carefully removing it from the mating surfaces. It seemed to go ok, they have never leaked etc but maybe it has caused this issue. I may have to search or a pair of used brembo 4 pt calipers.