Wow didn’t expect all this cheers mate
But yes I will definitely get the crankcase breather done! Can I advise on which one is the best on eBay UK as there’s so bloody many
As for the manifold I got the the exact same one u did the x8r cast iron one! And when they took the old one off it wasn’t actually that badly cracked it was about a 3mm gap so must’ve not been that in the first place! I also had a hole in the rear strorage compartment fixed above the back box to no avail also but least I got it done! As for the egr valve I had that deleted and left open on a re map of the x5 but I haven’t taken it off not sure if that is something I should do! It’s weird because with windows open it does it but with them shut it’s spot on

A 3mm gap (crack) is massive. Mine smelt bad with a 0.5mm crack (about 30mm long).

You might need to get a flashlight and a helper and have a good look around the manifold (with a mirror!) while the helper gives it a few revs - see if you can spot the source of the leak/fumes... but it will show up eventually, via soot everywhere...

Assuming it IS a leak... When you say "windows open" do you mean the car's side windows? Because driving with windows down at speed can create a negative pressure in the car that will pull in exhaust fumes from the rear... which is pretty "normal".

Which breather to buy? If you want the vortex design, there's a few good choices. I went with the BMW unit, like this one...

https://www.ebay.co.uk/itm/ORIGINAL-...AAAOSwm5NdrrDG

Febi Bilstein is supposed to be ok too -

https://www.ebay.co.uk/itm/FEBI-BMW-...5e0414f8c63200

Vaico is in the list too, I suppose...

https://www.ebay.co.uk/itm/BMW-DIESE...UAAMXQN8BSMs73

Not many suppliers off the older "loo roll" type now, despite it being a better filter (but needing more attention)… Meyle do one.

https://www.ebay.co.uk/itm/MEYLE-314...YAAOSwEcReN21Z

If I could get the Meyle one at a decent price, I'd go back to that and replace it every time I change the air filter (since you're in there...). :rolleyes: