Xr3i and RST both use the sandwich plate that houses the injectors. No manifold came as standard with Injectors straight in - people have modified them to take injectors however (tho usually EFI, i see no reason/benefit to do it for K/KE-JET).

Do you have a pic of the manifold?

I "think" some of the RS1600i lines were routed slightly differently to 3i/RST to the metering unit but weren't so different that you couldn't make them fit..