SanDisk Extreme SSD Firmware R211m download for for MacBook and MacBook Pros based on NVidia MCP79 chipset

go to applications > utilities > system info > SATA, if the SATA chipset is Nvidia MCP79 the SATA link speed will not be negotiated correctly. This is an issue with the Nvidia SATA chipset. SanDisk has not released a FW that locks Extreme II SSD to SATA 3Gb so the link speed will only be 1.5Gb. If you can find the original Extreme SSD you can use the FW linked in this thread to lock the Extreme SSD to SATA 3Gb.