Have you checked the intake boot for cracks between the MAF and the throttle body?
The MAF could be bad if you don't have any leaks.
The alternator output will vary depending on the RPM, the state of charge of the battery, and the load placed on the charging system.
If you were reading 14 volts it sounds like your alternator is working OK.
2000 540/6 Slightly tweeked...everywhere