Josh, you should have a check valve in the line going to the purge canister I think. Seeing as you work at a dealership, have you asked any of the service techs their opinion? Are you measuring the voltage on the O2 sensors from the ECU or are you looking at it as it comes out of the sensor? Have you swapped out ecus to see if it'll help? The TEC-II will take care of any O2 sensor problems in that it'll use its own o2 sensor. Is your idle bad or is it just throwing a code?