[Jackboyo]

The car is a E90 320D with M47 engine.
Just removed the inlet manifold to remove the swirl flaps, change the crankcase breather, new air filter and clean out the gunk in the EGR. Everything back together, engine starts fine.
Takes it out on a road test, feels sluggish and when pushing the accelerator down can hear the whoosh of the turbo as though there is a leak. Can smell it as well. Checked for any codes on INPA, this is what I get

3F35 Boost air hose monitoring idle running

Now the boost hose that fits on the front of the EGR was pretty tight coming off, now seems quite loose with the locking clip, so wondering if the seal in there is letting boost past? (BMW dont have the seal in stock, coming tomorrow)

Or could this message relate to something else?
What sensor picks up this fault?