Patrick, just a crazy idea, but swap the oft and right probes, wires, everything on one probe on the left and one on the right and see if the temps are reading accurately. If you move your #5 probe/wiring over to #6 and vice versa. If #5 (which is now in the #6 cylinder ) stays hot, then you have a measuring issue.
did you verify you have the right injectors installed on that side? Maybe something got missed there and they aren’t flying right.
you checked the induction system already for leaks, if I recall, right?
At low power cruise, full rich, are the temps more even? If so that probable eliminates a probe offset/bias issue….does the spread increase only as you start to lean?
what happens when you lean at say, 55% power, are you getting the same high temps in the CHT?
i hope you figure out out and it’s something simple…
don’t get discouraged. No matter how good the airplane, your first two years is full of surprises. By the time you get it perfectly right exactly how you want it, you’ll be itching for an Acclaim.