7mgte swap mk3 n/a turbo

Hey guys, I just recently helped a buddy do a n/a-> turbo swap in his Supra. First off, it is a 1986.5 shell, and we swapped in a 1990 7mgte motor with R154 including the wiring harness and the proper ECU. Now the only question i had was, everything plugged right in, BUT there is one small plug...