Any ideas? It is a 2004 Cooper, and at standstill with the engine not revving you can hear a fluffing/blowing noise from teh engine bay. Not disimilar to a leaky exhaust, but seem sto be from near the head. The exhausts look fine, there is no major oil leak (not lost any either) all pipes are still plugged in. Noise is predominant on offside in engine bay. Will take to someone but do not want to get ripped off. It reminds me of when my focus lost its oil cap.

Cracked exhaust manifold? Do you smell anything?

No smell of exhaust no feel of air sucking or blowing, but then it was a rather warm engine so will look again this morning

Could be a pre or post cat leak. That would be hidden under the heat shields...