Cracked manifold/faulty glow plugs?

[X5Sport]

It won't (at least it is less likely) be the plugs as they are sealed in.  A cracked manifold however will definitely do it as it will mean fumes can get into the ac intakes as they are only in the scuttle panel.

[Smeeagain]

And if replacing the manifold get a cast iron one off ebay not an OEM one as it will crack again
Smee

[gsj87]

How much am I looking at to get the manifold replaced? Rough price?

[Smeeagain]

a quick search on eBay for "E53 exhaust manifold" brought up this at £70.

http://www.ebay.co.uk/itm/New-Replaceme ... SwOtdYVAql

Perhaps goes without saying that it is your responsibility to check that this is suitable for your vehicle and I ma not endorsing that seller. IT's just to show you but it's comfortably less than a hundred quid

Smee