For me I found by installing a vacuum gauge on the drain plug of the air box that the OE pipe alone had enough restriction to show on that gauge starting at 3800. Just putting the clean pre-filter bag over it that it comes with didn't increase the restriction but letting it get a little dirty did. And all the modifications I did to that pipe had no effect on restriction.. let alone installing all those filters I has ported to the bed-side....that plugged-up is just a few road miles. The only thing that stopped that was when I got rid of it completely and went with the 2.5" turbo pipe and fittings to the right side of the bed and adapted-out to the 3" and stacks. Then no matter what filter I put in the inline can, I never got any measurable vacuum level on the air box. So...with that said, anything you put on or over the end of that stick intake pipe will increase the resistance and make more vacuum on the box..and engine intake system. For now I would box it off in back and either run it with no pre-filter or just the bag. Getting all it's air through the cab and grill will be an amazing improvement all by itself...for the engine and filter life.

Ok, so I am ready to make a mod to the air system of mine, tired of having to clean the filter after every single ride!  So knowing what you do now, what is the best recommendation to have the air all come through the cab instead of underneath the cab?  I had thought of drilling a 2" hole in the front of the plenum and blocking off the back one, then making it run through the grill, then block off all the holes in the grill.  Thoughts?

If I had to do it all over today,..I would do as others have and made a box out of 1/8" ABS sheet plastics that would seal off all air from behind the back cab plasitcs then replace the intake tube with 2.5" turbo pipe as I once did except..I would custom cut the front-facing side in a long angle..facing the grill. I would then just drop an Outerwears prefilter over it. I would loose the second filter I have and yes, I would have to clean the one in the air box way more often...but not after every ride at least. I do like filtering the CVT air out here as it stops all that BS build-up and worn parts...but it is a PITA cause the filter gets plugged very quickly sometimes. I'll keep what I have for now and eventually put the S&B on top...but it's getting pretty expensive and I still need another 400 for the S&B.

I'm going to try (because I have some) tacky secondary spray booth filter on the CVT intake. Maybe as a pre-filter on engine intake too. This material is designed to allow maximum cubic feet per minute (known as, "CFM") air flow as spray booths move a huge amount of air.

[2015 Z Force 800 53/Trail EPS]

I was thinking about the crushed adapter issue and it seems to me that although one might get a piece of ABS or PVC to work, the best thing is to use something as thin to maximize the air flow yet be so strong you never have to worry about it ever again. As I built all my intake systems with 3" and 2.5" aluminum turbo/intercooler pipe, to me some 2.25" would be just the thing to use here. For like 8 bucks you can get a piece of 2.25" x almost 20" from amazon. Way more then necessary but one could find some use for the extra down the road somewhere...or sell some to a buddy with a Z Force. I might just head-off a potential problem and get one of these now.

https://www.amazon.com/Rodin-Intercooler-Straight-Thickness-Aluminum/dp/B08T88RG9V/ref=sr_1_4?dchild=1&keywords=2.25%22%2Bturbo%2Bpipe&qid=1623105417&sr=8-4&th=1

OK so I did buy that long 2.25" pipe and it finally came. Today as I was working in the shop anyway I went a head and pulled the air box cover and filter...and adaptor. Although mine was only 2"s long without the end flange I saw that I could go farther into the rubber on the box-side and because the oversized filter I use doesn't have that lip inside, I could go a little longer that way too. Cut it at 3", cleaned it up and installed it. Worked perfectly. This is a safe mod to do and one that probably should be on your list.

Just what i needed.