Subaru legacy post 1995 ECU

[Ron & Cathy Webb]

I have a friend who is trying to install a 1995 Subaru Legacy
engine, with factory ECU intact, into a gyrocopter.

He has reached the point that he can run it on the bench, and
finds that after 3 minutes or so it goes into what sounds like
limp home mode. Not over 4200 RPM. He thinks this is related to
the OBD2 stuff. The ECU can't talk to the transmission, 4WD
system, ABS system, or whatever, and eventually decides there is
a TERRIBLE problem.

Anybody know how to tell this thing to "shut up and soldier"?