[Xeen]

Welcome to the board.
In cases where the documentation is saying one thing and a person you don't know is saying another then go with the documentation because chances are it is correct.
On the computer you need to find out if the transmission has it's own computer or if it is an all in one then you will know.
If you keep all the emissions in tact you will need all the wires in the harness but if you have your computer tuned to remove emissions then you will need to have the harness trimmed which in most cases the people who tune the computer can do.