I agree with Pichej. Chunk W of Wafer T90BX does have low amplitude and poorer yield. WPE came in wider than expected post tilt and amplitude for this chunk is far lower than the rest of the wafer. This is not HGA related, it is strictly wafer related. Amplitude was significantly lower for this chunk from Pi lot data but I missed that since I was focused on material close to WPE target and Pi lot yield was not terrible (50%).