I actually would try to find the issue now. Adding variables rarely simplifies troubleshooting.

It seems very common that codes triggered by an out of spec O2 reading end up being something other than the O2 sensor, so yes, I would not assume new sensors will fix it. Since your code said bank 1, pre-cat, you might try to just swap the two pre-cat sensors and see if the code changes. Those sensors are easier to change than spark plugs - should only take a couple of minutes - done from above.

Some data from my 2001 3.0i that may help:
Intake boot, 13-54-1-440-102, was replace by the PO at the dealer at 158k miles. Then at 184k miles, I got codes P0171 and P0174 (bank 1 and 2, system too lean) which I easily traced to a ~1" tear in the intake boot. Replacing that fixed it. So for me, that boot only lasted 26k miles and 5 years.

I replaced the original pre-cat O2 sensors (Bosch 13477) soon after getting the car at around 169k miles in a futile dream of improving MPG. No codes before or after, no change when putting the new ones in.

EDIT - also I noticed you say it is in an X3. Do you know what differences there are between the M54B30 in the X3 vs. X5? (and my part numbers above are for the X5)

Ok good advice, I think I'm going to pull the intake boot and have a look, also thinking of putting in a bottle of fuel injector cleaner. Thx again. I will update as I figure it out.

If the 02 sensors is indicating a "Rich" condition they are fine. You can verify this with a scanner that can read real-time data. The front sensors before the cat should show a variation in the voltage, while the voltage at the back of the cat should be constant.

Why do people always blame the 02 sensors for a rich or lean condition?

This just tells me that they know nothing about how to fix a car.

Here's a video on good 02 sensors on an X5.

https://www.youtube.com/watch?v=zyh_4SktmFM

Here's a video on Short term and long term fuel trims plus voltage on the 02 sensorshttps://www.youtube.com/watch?v=WMSM7WAbBss before the cat.