Apparently you can overclock the GTX 1660 Ti VRAM an extra 1000MHz and it's perfectly stable. I've played FarCry 5, COD BO3, and Minecraft with SEUS PTGI all for a few ours
How is this possible - GTX 1660 Ti VRAM Overclock grew by +450Mhz | TechPowerUp Forums
Introducing GTX 1660 Ti: The Perfect 1080p Upgrade