I believe the XN6 engines were the same til the end of '85 . If one were to
put in a new engine
the '86 would be preferable . The polution stuff in the exhaust was
eliminated with
the change to the heated oxy sensor. I have not performed this transplant
but it
should be straight forward maybe someone has done it. Also the head bolts and
block were changed so anual retorquing weren't required.
Bob Bruce 83 STI Xn6
84 STI XN6,GL ,GL SW, S
85 S SW
86 S, GL SW