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P0204

2001 lq4/4l80E, 500hp unit. BTR stage 3 cam. I've had the system for about 2 years, finally been running as my daily for the last 4 months. Last week developed a rich issue, rough idle. Twice, hard start. The only related code is P0204. On the LS system, which is considered #4 injector? I've tried unplugging all the injectors on the passenger side but didn't notice anything different.  Today, it started it again. I could see my AFR running rich. My sensor is in the driver side. The only info I've found here is related to throttle bodies. Did Fitech number injectors differently? Or in relation to OE specs? Thank you.

If it's been running as your daily for four months, you had it wired correctly.

Try changing the o2 sensor to a new one.

While you're at it, add the second o2 sensor so the ECM can control the fuel side to side, not all as one.