P0135 Code after x-pipe install

I need some suggestions. I recently installed a VRS o/r x on my car. I used plug in MIL eliminators to keep the CEL from coming on, but no luck, the car is throwing code P0135 Upstream Heated Oxygen Sensor Heater circuit fault - Bank No. 1. I have inspected the front O2 sensors for damage, or to see if the wires are damaged and everything looks fine. The car is surging at idle, and I think it is running rich b/c my gas mileage is terrible. Anyway, should I look at purchasing new O2 sensors or would getting the car tuned turn these off. I don't want to spend the money on the O2 sensors if in the end getting the car tuned is what will ultimately fix the problem. Thanks for the advice.

1996 GT conv. 70mm tb, CAI, VRS o/r x, Magnaflow exhaust, eibach pro kit, Tokico hp's, MM cc plates

tonytaylor85 said:

The downstream (rear- and MIL eliminated) O2 sensors have nothing to do with engine tuning, they are there to check the catalyst and the upstream sensors. If the code says upstream (front- which the code says it does and agrees with your poor idle and mileage) then your X pipe has nothing to do with the problem. The front heater circuit is at fault so check the fuse. If the fuse is good, check the two white wires on the sensor with an ohm meter. If it reads high, the heater is blown and it must be replaced. I recommend replacing them in pairs.

Also- are we sure that you have the MIL eliminators in the rear O2s and not the fronts?

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Thanks for the info. I put the MIL eliminators on the rear O2s and not the front. When you say the front heater circuit, do you have a part number for this or is this something that would be part of replacing the O2 sensors. Also, which fuse is the correct one to check? Sorry for the stupid questions, I'm still learning my way through this.