I am just getting ready to do this swap and was wondering can i use a harness from a 88 Si for the dpfi to mpi conversion or is it easier to convert the DX harness.

 

the only way you can do it is to convert your stock harness to mpfi unfortunately. if you just tried to drop in lets say a 90 Si harness although the engine harness would be setup for mpfi, the harness that went into the car would not have the proper wiring for mpfi to function. thats why during the dpfi to mpfi swap you have to run wires from the engine bay into the car so that you can splice into the ecu. unless you like replaced your entire interior harness then droppin an Si harness on the engine will not work.