There has been a post about this previously. The XR3i pumps and RST pumps are different. They flow different pressures.

The XR3i flows at 4.7 - 5.5 Bar, see below



And the turbo flows at 5.5 - 6.0 bar, see below



May need to load pics externally as they are resized and somewhat inreadable.

The XR3i pump will work but the maximum operating pressure is being used to cater for the RST fuelling. If you are running anything over standard then an RST fuel pump would need to be used.

IMO I would just go a pick up a cossie one on ebay!