Alright my ECM is gone on my AWD and I am looking for a replacement.. and I have one but I don't know if it will work.

So here is the story, I got the computer out of another 90 TSI but the wiring harness at some time had been swapped (don't know if it was from another 90 or some other year or what). I also have a 93 TSI computer. So my question is will only another 90 TSI computer work in it since I have been told 90 is different from the other years or will some other computers also work? How can I tell if the ECM is a 90 or not without plugging it in. Will the car run at all with the wrong year ECM? Finally how much would it cost to have my origional ECM rebuilt? Thanks alot guys