I did an aristo swap in my 2000 gs gs300. I need to know what the extra grey plug on the ecu is for and also need to know if the missing body plug is going to be an issue. Is it also necessary to change the orange and black body plugs

 

Grey plug does not get used, missing body plug is fine, and yes you need to use the orange and grey plug that came with your aristo harness. I just did my swap and have a 10+page write up on it. Go through it and there are plenty of picture's in there that might help you out.
Good Luck

 

I didnt get the orange and grey plugs with my harness

 

Damn, that suck's. Where did you get your engine from? If it was an importer, you can call them and ask them to send a set to you. If not them you going to have to find the thread on how to do the re-wiring. There is also a few good people on here that know how to do it. Im sure if you ask they can help. Im sorry, if I knew how to do it I'd help. Ill see if I can find the thread and tell you how to get to it!

 

Look for "SBM2jLEX" post on his swap. Its like 16 posts down on this page. Look for post #133, there's 2 pictures there that show you how to set up the wires.