Check engine light came on. Had it checked for code at auto zone. Said right bank is too lean. Replace 02 sensor.

I changed sensor and light stayed off for 50 miles and then came back on with same code error. I changed spark plugs, air filter and put seafoam in fuel tank and filled up with ethanol free gas. Same problem with light still on and engine doing some surging and not the usual smooth power I am used to. I bought the car new and have had it serviced on a regular basis. It stills says right bank too lean?????