2000 Mercury Villager Runs roughly and stalls

Has run great up until some time ago, when it started driving roughly only in wet weather. Now in dry weather, it starts fine, but drives roughly after warmed up (15-20 min) and then stalls. Will restart, but dies again shortly. Codes said oxygen sensor, knock sensor & cylinder 3 malfunction. Was told knock sensor code could mean it needs a tuneup. Changed spark plugs, wires, distributor cap, rotor, air filter, gas filter, oxygen sensor, PCV valve, cleaned EGR valve, replaced some vacuum hoses. Still runs the same. The knock sensor code still shows. I am in Mexico right now and can�t get a knock sensor. What do you suggest? Thank you.