What part should I replace EGR Valve or Oxygen sensor

If the van starts and runs I wouldn't do anything until a couple tanks of gas

Thank you for responding. CJSRAS I took the van by O'Rielly Hector that work there scan the van he didn't give me the codes he just said it was the erg valve he said that was all that show up then he advice me to have it check out by a mechanic before changing it. well i gave the run down to my mechanic and he the one who mention oxygen sensor he told me to reset it first so i disconnect the battery and reconnected drove around the block did good then the light came back on went back to O'rielly had it scan again once again hector didn't give me codes he just mention my seat belt,cylinder three misfiring and erg value the other two was nothing new so then he reset it with his scanner i drove my car around it did great all the way to home then next morning it came on again. so that the end so far i have noticed something new..........Tom my van was full with gas had about 350 miles left for traveling i made a few errands that would have left me aquarter of a tank left i am complete on empty with 25 miles left what ever wrong with my can i felt like it suck the gas away i couldn't believe it.............Old storqnpower the idling is good

oldstorqnpower...thank you for responding. will the erg valve have anything to do with my gas? what does the erg valve do excatly for the car and what the side effect from it Now on the cylinder3 the mechanic broke the plug inside finally half a day went bye he final got it out he said it has been threaded before to me understanding he had to thread it again after the work was done the check engine kept coming on so ignore it .......it recently came on after my daughter run the van out of gas but then i was told it would not make the check engine light to come on so back to the question should i test the coil pack first which i forgot how. I have to look it up again or i should just go ahead and replace the whole coil pack? I have new plugs new wires new cooing fans new alternator new water pump new starter new battery new gasket upper and lower intake new belts new tires 5 new tire rods and eliamate it just seem like I got a van full of trouble if i didnt need this van i would get rid of it but it important to me cant afford another one right now

Who is the mechanic who did the work? Are they certified and trustworthy? It seems like they would have done the repair correctly and for you to still not have a problem.