I spent five hours the other night trying to diagnose what I thought was a bad vibration pump in the Silvia. This is an older model but still a remarkable workhorse. After disassembling the pump and descaling, the flow from the group head was still very low. I took off the shower screen, and found it was completely plugged. After cleaning that, the flow was still bad. This is when I discover quite by accident that the “group head jet breaker” is removable. It fell out while descaling.