Told ya I'd get argument. And i'm not disagreeing with the intent/design of the sensors, but I can tell you from experience with multiple vehicles (interestingly, all chryslers, and all NGC 4-plug equipped vehicles) when the downstream O2 sensor has problems weird things can happen. I get it it's a sample of 1 person, but considering (for at least my 2007 KJ) the upstream and downstream sensors are the same part number, and they're $25.79 over at rock auto, doing all 4 at once isn't going to break the bank. If anything I'd be more worried about the cat connected to the glowing manifold. edit before post: I just looked up a 2002 on Rock Auto, and it has 4 different part numbers for each of the 4 sensors. Wild.