Check engine light comes on during hard braking, no codes?

7730 ecm running $88 mask, egr, dizzy retrofitted into fiero 2.8.

The check engine light illuminates when hard brake condition, stays lit until key off, No codes, disappears with key on again.

Tuner pro showed "egr error", but no code and all three solenoid show "ok".

Any ideas?

The bin is bawx adapted to a 2.8. Maybe some test needs changed in routine to work on smaller flow engine?

Brake booster check valve leaking?

Great suggestion! I also noticed the iac counting 50 steps at idle. I've instructed the owner to adjust out to 20-30 steps hot idle. I liked the booster suggestion better, though. I overlooked that one completely.
Ron