Super rich condition... Codes inside

[Bad89stang]

My father-in-law's 92 has had a recurring problem with a rough idle and rich condition while at idle.

Fuel pressure has been checked. We have tried both 38 psi and 40. The condition exists with both settings.

Timing is set at 14 degrees.

No vacuum leaks present.

O2 sensors are less than a year old.

KOEO codes show:
34 (EGR)
KOEO codes show:
34 (EGR)
The rest are kind of vague, but we seem to be getting an O2 sensor code (rich/lean condition) occasionly. The codes are kind of hard to make out. We have the tone type reader.

Could the EGR valve cause such a rich condion? I know it can cause a rough idle for sure.

If you stand behind the tailpipes, it will burn your eyes from the fumes. The car runs great when you get into the throttle.

Any ideas before we start replacing parts?