I was able to run the cylinder compression test while the engine was at operating temperature:

Cylinders 1, 2, 4, 5: 160
Cylinders 3 and 6: 170

Those are decent readings, right?

Also, thank you @TryX5 and @Henn28 for the advice on cleaning/drying out the harnesses near the driver side of the radiator. I cleaned/dried that big plug going into the ABS unit and that seems to have cleared a few errors!

The mysfire is still on cylinder #5. But what is interesting is that the mysfire only shows up after I try to drive a bit aggressive. If I drive it without any hard acceleration it doesn't seem to occur.

What should I look at next to figure this out?

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2001 BMW X5 3.0i, Automatic, Gasoline