Mac Pro (2013) CPU & Riser card bus bar screws torque value

Are you referring to the 4x bus bars that attach and ground the CPU to the PSU? if so, it is the following:

Bus Bar to PSU Screws

Use the torque driver with the T8 security bit to install the four (4) T8 bus bar screws (923-0712) to 7.5 inch pounds (in.-lbs.) or 0.85 Newton metres (Nm).

Bus Bar to CPU Riser Screws

Using torque driver with T8 security bit, install two T8 bus bar screws (923-0716). Tighten bus bar screws to torque value of 10.5 inch pounds (in.-lbs.) or 1.2 Newton metres (Nm).

If you are referring to the CPU heatsink and locking bar, its as follows:

Using torque driver with a regular T10 bit, install four T10 screws (923-0707) in sequence shown until all screws are tightened to 10.5 inch pounds (in.-lbs.) or 1.2 Newton metres (Nm).

I hope this helps.