I recently bought a 2004 Subaru Impreza with a 2009 legacy 2.5l N/A engine swap. I'm new to Subaru so I have some concerns. Unfortunately the mechanic that did the swap has a 1.6l intake manifold, harness and ECU working on the 2.5l. I want to change this to the original 2.5l manifold which I have in my possession but I don't have the harness or ECU. My concern is if the 2009 2.5l harness would work in 2004 Impreza (dashboard connections etc) and how I would know which is the correct 2.5l harness and ECU to buy. Can anyone advise?