Printed with P1S with AMS.
Personally, I used supports and printed it flat side down, but the supports go under the vents and are very difficult to remove.
I suggest angling the whole thing so that the vents print mostly vertically. If done this way, you should only have supports on a side that isn't seen (albeit a lot) and are fairly easy to remove.
Gundam_Chest_Vent_for_Harrier.stl | 41.6KB |