As with all things that I haven't done before, but find that I need to do to overcome some obstacle, I'll have to do some research, and devise a method that I can use in my garage.
I do, however, believe that I can use casting plaster to create a mold that is split along some axis that allows for the extraction of the cured silicone rubber, without resorting to invoking blue incantations of technical frustration. An interior mold-piece will probably have to be made, and I don't have an instant method for that.....yet....but, if I have to go that route, I will spend enough time on it so that I come-up with something better than being PO-ed at Toyota for yanking those part numbers from the pipeline.
I've actually had some very good past successes in creating some very good replacement parts for a variety of different things, over the course of my lifetime, but have always just kept my mouth shut about it, thinking that it's so obvious that anybody would do similarly when confronted with the same problem. However, having had my wife cajole me over the years about this kind of thing being non-obvious to many people, I'm just tossing the idea out here in the spirit of helping others with the same problem, and it'll be what it'll be.
Since there is an intake resonator present in the air stream, I presume that there are critical specifications for the physical dimensions of the hose, and the "flexibility" or possible lack thereof (it is a pretty stiff hose, after all) of the hose may preclude the use of un-reinforced silicone rubber for a successful end result. If putting a more flexible hose into the intake stream has a negative affect on performance and/or mileage, then I have my answer, and will have to shop materials to use for casting.
At the end of the day, despite my best intentions, I have some good ideas about how to get started, but I'm flying by the seat of my pants on this one....hopefully not with my hair on fire.