I had 18" Kumho Ecsta SPT in my 159 (tyres bought used in spring this year with 18" horeshoe alloys). They were bit too noisy, and annoyed me a bit all the time. They also around 80km/h (50mph) could cause kind of slight vibrations and loutder noise which disappered when I bit only changed the speed. It turned that although they had plenty of thread (like 7mm), 2 of them (ones I put on back) had heel-toe thread - probably previous user had someting wrong with dampers or other car issues and damaged the thread that way. I changd them to GY F1 Assy 2 months ago, and now it is quiet. In my case on corners/roundabouts they got louder - thats why I thought first it is bearing noise, but when I lifted the car, I could not feel any problm with barings, and then realized it was heel-toe thread but in my case was mainly at outer side of tyre only.
It is quite easy to check with closing eyes and sliding your hand both directins through thread (easiest if you have wheels demounted, but possible if you have them on the car). If you feel one direction goes harder and feel steps, and other goes smoothly, then it means rather heel-toe damage of tire. The problem with Kumho Escta SPT is that it is directional tyre and not much can be done to repair it. If it was assymetric tyre, it would be possible to swap left with right wheel, and try to cut the heel-toes by just driving say for another 1-2k miles (so the heel toe attacks the road surface and gets lowered over time).