You have a potential land mine on your hands. The N62 is one of the worst engines they every produced. If you are going to keep this car, which I would encourage you not to do, you need to get a scanner and find out what is going on. There are so many potential reasons you are having the multiple issues. IT could be simple as your MAF, but you are shooting blind without starting with a scan. And not a generic auto zone one. You have some time and major expense ahead of you.

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Dave S.
Northeast
2003 4.6is
2005 E53 4.4
2003 E39 Msport(a REAL ONE!)
1959 Fiat 600