Try the ECI Nickel Carbide Cylinders.
My engine is a TCM IO520F.
I have tried Millennium cylinders which went half life and required a top overhaul due excessive oil consumption. I had a greater fuel endurance than oil endurance!
I installed a set of ECI Nickel Carbide Cylinders at the next overhaul. At about half life the cylinders became subject to a 50 hourly AD for cracking due the problems experienced with the regular cast iron bore cylinders.
My cylinders never did crack and went 1800 plus hours and at overhaul showed no wear at all. Cross hatching was still visible in the bores. There was no lip at the top of the stroke and leak down tests showed 74/80 psi at the last 100 hourly prior to overhaul. The overhaul engineer said he could probably re-install the cylinders and they would do another 1800 hours.
I subsequently fitted the same cylinders at a price cheaper than Millennium or TCM. The current engine is at half life with leak downs showing 74-76/80 psi.
I would recommend them as a superior product.