Petrol smell on cold start

[john_p]

E46 328i - Noticed a few times there's been a petrolly smell in the cabin and around the engine on cold startup.

I took the injector/fuel rail cover off last night and had a good look about, no signs of leaking petrol from anywhere, checked where I could with ignition on and engine on, back to the fuel filter.

The fuel hose/rail connectors (at the back of the engine) were dry but the plastic "latch" seemed to be loose, is this normal? Couldn't see a lot there.

Thinking some sort of air pump or emissions control maybe? Anything else I should check? I did notice that the rectangular box attached to the side of the inlet manifold was making a bit more of a noise than I remember, but I don't go under the bonnet that often...