I'm changing the air filter on my 2005 156 JTS and the three bolts holding the top of the boxare knackered. I thought it would be easier to sort it out on the bench than leaning over the car so I'm trying to remove the box,which is connected to another one under the wing by what looks like a short stump of pipe. So far I've removed the bracket holding the filter box to the battery tray and the bolt that fixes the other box under the wing. I can lift the lot so that the posts on the bottom of the filter box are clear of the fixing holes that they drop into. Side-to-side movement is limited by a couple of pipes underneath that run between the two boxes but there's a good few inches between the filter box and the radiator, engine etc and there's an inch or two between the intake pipe and the bumper. So the two look like they should just pull apart...but they won't.
Here's pictures from below and above. Does the one from above show some kind of twisting, locking mechanism? If so, i can't see any way to rotate the boxes to unlock it as there just isn't room.
Answering my own question after a fresh look at the problem, in case it's ever useful to anyone else. Those slots (one top one bottom) are not twisting locks but tabs that you can press in with a screwdriver and then the inner pipe will slide free of the outer one. Just don't press them too hard or else they...err...break.