hello everybody, have a little problem here. a guy at work has this Explorer with the 4.0 V6 4x4, (not the overhead cam), 115,xxx miles and the CEL light was on. took it to Advance and got it checked. came up with 2 codes (can't remember exactly), but it was both right & left bank upstream O2 sensors with a lean condition. we put in a can of seafoam, filled it with gas and i reset the computer, (disconnected the battery). he has drove this vehicle almost 500 miles and today the CEL came back on. is there anything in particular i should look for or just go ahead and replace both sensors? it has had a new fuel filter put on about 3 months ago, and i put in new plugs and wires last month. any help would greatly appreciated. Thanks