I'm looking to swap a 1990 S5 N/A motor into my 1988 GXL S4 N/A. I need to know which way works best. Swap the S4 intake manifold complete to the S5 motor and use The S4 ECU. Problem is that the S4 motor has a EGR valve bolted to the block and the S5 doesn't have that port. Or do I swap the whole S5 including the wiring harness and ECU and the deal with modifying the harness to fit the GXL front cabin wiring harness so the instruments all work and the ECU doesn't cause a check engine light. I need it to pass California smog test. Any help appreciated especially if you have done this swap before.