hey mate
i dont think they make a loom for the rb20 they all seem to be for the GTR
i did exacly the same thing ordered for the rb20 but got the n-4 loom, so what i ended up doing was changing the wires over, from memory it is just the ignition and injectors that you need to change and it is just the order that needs to change, what i did was grab the rb26 pinout from greedy and compared that with the rb20, and also used the ignition and injector diagrams from the manual. i cant remember the exact wires it was but i know it was only 8 that needed changing and was easy enough to change. dont touch the AFM the right one is already, power earth and throttle are also right. once you have done that there are a few paramaters that need to be set on the emanage and it should be right to start up. if you get stuck let me know as i have just setup my emanage on my r32 and have everything running.