No, I've not seen these applications, and if I had, I'd protest, just to see the creative excuses used for adding them. I personally don't think you can claim they are legal, but I have read of people who have done this, and defended their use of it as radiator ducting/shrouding. But you better be prepared to argue your position, and defend it, rule and verse, or don't bother. That means, you need the rules book if you don't have it, and you need to understand how IT rules work (if it doesn't say you can, then you can't)
As for cone filters, HKS has an adapter for adding a cone filter to the AFM, 20 bucks or so. K2RD had that for sale a while back, dunno if they still sell it. I found mine on a junkyard RX-7 that I bought from there for 5 bucks. 40$ K&N filter, and awaaaay I go.
You also have to find a way to mount the AFM solidly, once you remove the air filter box, the AFM is loose, and you have to find a way to mount it. I used some bent aluminum strip and a welded bracket to hold it on.
The 89-91 AFM can mount a cone intake directly on it, but you'd have to swap to an 89 electronics setup and that's more trouble than it's worth. But if you already have the 89-91 setup, this should be fairly simple.
Home Depot Racing