After Apple released Apple Mac Pro EFI Firmware v1.3 on 3/27/08, the Sonnet Tempo SATA E2P card no longer worked in slot 2 of the Mac Pro Early 2008 Model 3,1. Slot 2 is a x16 PCIe 2.0 slot. The solution is to move the Tempo SATA E2P card to either slot 3 or 4, which are x4 PCIe 1.1 slots. The Tempo SATA E2P card works fine in the PCIe 2.0 slots in the Mac Pro (Early 2009) Model 4,1.
Unfortunately, not. The driver was written by the 3Gb SATA controller chip maker, Silicon Image, and they no longer maintain the macOS driver for this chip.