1999 4runner limited emission problem

i believe i need new o2 sensors. can i use universal type sensors, or should i stick with the specific sensors for before and after the cat converter? if that is the case, what is the cheapest prices you've seen for o2 sensors? Thanks

Check out the major chain parts stores for prices.

Car part stores like AutoZone sells them for $128 per piece.I think on internet you can find them for $105 plus shiping.