O2 trouble codes

O2 trouble codes. Slight surging (speed) on highway

Hello, I recently replaced the original never-changed 02 sensors. No prior problem, mechanic friend said they should be replaced.

Check engine light comes on after 2-5 minutes and codes 1 and 2 flash on the ECU. Slight surging on the highway at 65 mph but no discernible rhythm or pattern to it. Random.

Checked sensors for contamination but none that I can see. (Can send pic.) Connections seem ok. Do not know how to check output from sensors.

Wrong or bad aftermarket sensors? (There are two; both on exhaust manifold.)

Replaced EGR valve yesterday after trouble code 12 that I ignored for many months. Seems to be more power now than before.

Starts, idles fine.

Richard