The first of many questions Im sure:

Ok I got my hands on a 04 STi long block w/ECU and harness, Im going to swap into a 02 RS. Im gathering info while I get cash for parts ( trans-FMIC-fuel stuff-ect... ) to do this over the winter.

Can I splice into the RS harness while using the STi as a donner? or Do I need to totaly replace the RS harness w/ the STi ( argh!..... I do not want to think about a full harness swap ) but if I must, I must

I have looked for hours on here over the past few days, and cant seem to find anyone who has done this perticular 04-02 swap. I know it all bolts up and it all fits. The wireing is the only thing I belive that I am sketchy with

 

Actually, the fact that you're putting it into the same body style makes it easier. You really don't want to consider disassembling both harnesses and then splice them together, trust me You just need to pull out the dash and everything behind it, remove the current harness and replace it with the new one. Look at it this way, everything will fit properly since it was meant for that body style and this way it doesn't require any wiring, more or less plug & play.

-Adam