Got the new upstream sensors in. I didn't clear any codes. The little orange engine light is still burning. Drove it about 9 or 10 miles tonight while we had an ambient air temp of 57 degrees. First 4 or 5 miles no issues, then it started the stumbling and chugging whenever I accelerated hard or went uphill. It may just be because we're having a relatively cool night here, but it still seems about 90% better than it was before. Time will tell with that I guess. I will clear the DTCs and rescan. Maybe possibly it needs a chance to learn the new sensors. If this doesn't cure it, I guess I'm on to checking for vacuum leaks, VANOS issues, or the (don't wanna say it) CAT. I'll disregard the oil on the post CAT connectors, since as Andrew says they don't affect performance. Thanks guys.

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2009 X5 3.0
2001 X5 4.4 - Sold