I got it to work but I also had trouble. One thing I noticed was the timing had to be right, the 2 machines had to be doing their network stuff at the same time or it would fail and just go into single player mode. Try making sure they are both progressing through their startup stages at the same times, either by launching them simultaneously or adjusted if one is slower than the other.
Had to get a new vid card for one of machines, just got it today. Was able to test again and now it works. I think my issue was the config file on one of my machines. I noticed the text was all pushed together vs my other machine config file. After adding a copy of the other machine config file and changing the seat number, they both linked up! Just want to say thanks for your help and thanks for your reply here/over at the other forum, if that was you there
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On another note, have you linked Initial D4 export? Did they same adjustments, but no luck. This game don't really show the little icons at the top like the other initial D's to tell if you're linked up or not.