if you have a DX chassis harness from the ECU to the firewall, you need to use a DX engine harness and do the DPFI to MPFI wiring changes - the DX chassis harness has no wiring in it for the additional 2 injectors on the MPFI and has no wiring for the Cylinder sensor in the distributor - these are the wires that are added for the MPFI swap -
to use the HF engine harness, you need a HF chassis harness from the ECU to the firewall - HF and Si engine harnesses are not interchangeable (although they will plug in) - all of the wires (except for one) in the driver's side connector are in different locations in the connectors - the HF has the igniter wire in the driver's side connector - the Si has the igniter wire in the passenger side connector