I have had a persistent CEL on this 91 Corolla. The code flashes 71.
I had the EGR valve cleaned out, and the EGR Vacuum Mod. filter cleaned. The Code cleared, and all was fine. But when Engine reached Higher operating speeds... The CEL was back. I checked the continuity of the VSV for the EGR, and it was in spec. I don't have a vacuum guage, so I didn't do some of the other tests suggested by the repair manual.
The short hose that connects the EGR valve to the VSV seemed suspect, so that will be replaced next.
Any other ideas as to what could make this problem go away?