AC130H - Identifying unknown parts

In many model kits, we are often confronted with parts that make us think "What the hell is this part?". We start looking at photos, references, subject documentation, and still find no reason to attach said piece of plastic to the model, especially if it looks weird and out-of-place.

Usually, these are optional parts, but it baffles me how often they are simply omitted from the building instructions, leaving you to wonder why they exist. Old incorrect parts, that were fixed in a re-release? Intended for future kits for a slightly different version? Who knows ...

I had this issue with multiple parts on the Chinook, and simply did not install them. On the AC130H, I now faced the same problem. On page 10, some kind of "box" is supposed to go over each engine. It's exact placement is hard to deduce from the drawing. Is it supposed to fit over or after the engine? What does it do?

On the model, they look a bit weird and not really part of the engine setup.

 You can see straight through it and I have no idea what it's for.

The box-art shows no trace of anything behind the engine (see previous post).

Google is your friend.
I started looking at my reference photos and blueprints and could find no evidence of anything being there. Until suddenly, I started finding photos that did appear to have something box-shaped behind the engines.
It wasn't until I added "engine" and "shield" together to the search terms, that the solution presented itself.

The answer!
Starting with the 130U, IRSS (infra-red suppression system) was added to mask the engine's heat signature, thus reducing it's visibility in the infra-red spectrum, used in sensors and (more importantly) heat-seeking weapons. The 130H appears to have been retro-fitted with the same heat shields.

So, now we know what it is and we have found photographic evidence that it was used on this version, I see no reason not to use these parts.