I have a 2000 3.8L V6.... I just recently purchased the car. When I got it, it had a set of longtube headers on it. As such, the previous owner had deleted the rear o2 sensors and put in a set of MIL eliminators. Shortly after I got the car, it threw a code for the upstream o2 sensor bank one, but no other codes. So I put in a new upstream 02 sensor and that fixed the problem, that code hasn't been thrown again... But immediately after I put the new sensor in, the car began throwing codes for both downstream o2 sensors(P0146, P0156)... So I'm wondering if anyone has any ideas as to why replacing an o2 sensor would suddenly cause both MIL eliminators to fail. I appreciate any help, I'm trying to get this thing through emissions.