Oxygen Sensor Voltage Readings and Possible Misfire at Idle.

[Philbar715]

I have an 05 GTO A4 with the following mods, Long tube headers (no cats, stock piping to straight through mufflers), over the rad intake, no MAF, SD tune, ported throttle body and intake manifold. mostly all tuned by myself. I say mostly because when i bought the car it already had been tuned by one of those predator tuners, basically the only thing I kept from that predator tune were the spark tables.

Recently ive noticed a stumble/misfire/hesitation at idle. It seems to happen the most when the outside temp is in the 50s and the car is still warming up. However i have noticed it when the car is fully warmed up. I notice it only when stopped or slowing down (less than 15mph). Its like the whole engine shutters for a split second then goes back to normal. Almost like an ignition misfire but all of the cylinders at once, if that makes sense. Only once or twice have I noticed it stumble/misfire off idle when giving it gas, then it was more noticeable but recovered quickly once it got past ~1000rpm.

Here are things ive done within the last 6 months, and all of these items have less than 1k miles;

New spark plug wires
New NGK plugs
Long tube headers
New upstream o2 sensors (downstream deleted and removed)
cleaned air filter
very mild adjustments to the VE table
Pulled codes; nothing out of the ordinary (MAF codes from SD and EVAP codes from evap system being unplugged and used for analog wideband data)

These are things I plan on doing this weekend;

Pull plugs and inspect for damage/lean/rich conditions
inspect plug wires, ignition coils and coil plug wires for damage
Inspect o2 sensors

Ive attached a couple of logs from a quick run this morning, it was cold outside and roads slightly dam so there are quite a few times where it spun and TCS kicked in. One of the logs doesnt have wideband data but the other one does. Also attaching current tune.

My questions are below;

Does the data (o2 mv) look normal from both sensors? To me it looks like one is more sawtooth/jagged than the other and thats probably not normal, indicating a bad o2 sensor or bad wire somewhere.
Can a bad o2 sensor produce the symptoms that I described above with the stumbling/misfire like conditions?
From the attached logs, are there any glaring issues that stick out to anyone?

Thanks in advance!

19-02-08 07-22-21.hpl

19-02-08 07-15-03.hpl

modified tune 2005 gto - Begin SD.hpt

[Lakegoat]

Under airflow, make the dynamic re enable to 7900rpm. Your ve table needs some smoothing. Look at it in 3D mode. Your base running airflow looks like it could use a little more in the 200--800 rpm area because of your mods. Those 1.00 and 2.00 numbers in base running airflow should be increased to the same approx. values as the numbers around them. That can cause a little stumble. Looking at your logs, you are a tiny lean in most areas. Your O2 sensors look fine to me.

[Philbar715]

Under airflow, make the dynamic re enable to 7900rpm. Your ve table needs some smoothing. Look at it in 3D mode. Your base running airflow looks like it could use a little more in the 200--800 rpm area because of your mods. Those 1.00 and 2.00 numbers in base running airflow should be increased to the same approx. values as the numbers around them. That can cause a little stumble. Looking at your logs, you are a tiny lean in most areas. Your O2 sensors look fine to me.

Ive cahnged the dynamic re enable to 7900, I'll work on smoothing the VE table a little. I cant find the base running airflow table, I see under Idle > Airflow > "Airflow final minimum". Is that the correct table to edit?

[Philbar715]

Just wanted to drag this up one last time. I checked the plugs and all of the gaps were fine, however in one of the plugs there were a couple of hairline cracks in the ceramic insulator. I changed that one plug out and its been running great ever since.