fwiw ... i have P0491/P0492 codes that I believe are due to a bad vacuum line (rotted then damaged during a Valve Cover Gasket replacement). However, I have the 3.0L so this may not apply. I have had the P0174 (too lean) and this was a whole in the large rubber air intake elbow between the MAF and engine. Good Luck.

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2003 X5 3.0 - Original Owner