'86 Accord LX-i
Thus far I have done the following in my quest to make the light go off:
Swapped EGR valve with a known good one. (holds vacuum, sensor goes from ~1.2VDC to ~4.3VDC when vacuum is applied)
Cleaned tube running from exhaust manifold to intake manifold
Checked the 3 port dealy in the black box
What's next? I'm about to douse with gasoline and light it up.