2000 Hyundai Sonata Super surging

This car has a serious surge problem. My code checker says both O2 sensors are malfunctioning but the owner says he replaced them not too long ago. I've worked on a lot of cars and replaced numerous O2 sensors and I haven't seen O2 sensor errors cause such a dramatic and rhythmic power surge. I would guestimate that it increases horsepower ~30 -40% and does so at ~ 3 or 4 second intervals. I've already asked you guys how to check the fuel pressure (since there is no pressure fitting in line). You explained how to do it and I did it and the fuel pump produced plenty of pressure (~45 psi). The surging is much worse when the vehicle has just been started but is still noticeable when its fully warmed up. I also replaced plugs, wires and a coilpak on it since the code checker said it had a miss on cylinder #2 (that's gone but it still runs terrible).
I tried some mass airflow cleaner spray on the MAF sensor and it seemed to help quite a bit but it quickly went back to running like poorly. Could the MAF be bad? They're expensive as is just about every other part on this car. I've also checked for vacuum leaks both by ear and spraying either and could not find any leaks. Any suggestions would be appreciated.