OK, it's time for an update.
First, I found a way to adapt the filter to the OEM hose ducting with NO RESTRICTION!! Hehehe-- duct tape. Laugh if you must-- I am! What struck me as funny is that I've used duct tape for everyone EXCEPT a duct! So it never occurred to me to use duct tape!
Anyway, the previous setup was a noticeable restriction. The 90° elbow closed off the effective duct area. To see for yourself, look straight into a glass. Then slowly tilt the glass and notice how the "window" into the glass slowy becomes an elliptical shape. Finally, as the glass is tilted to 90° from where it was before, the effective "window" is closed.
Duct-taping the OEM hose INSIDE the outlet of the POwerCore filter not only got rid of the restrictive extra plumbing (with the adapter, kink and all) BUT it also got rid of any and all fitment issues. It fits PERFECTLY now-- with probably even a little more space than a traditional BHAF.
Putting the OEM hose inside the filter also gives you more effective flow area. This is the LEAST possible restrictive way to use the OEM intake hose. Any other way involves some kind of insert inside the OEM hose, and this reduces the effective flow diameter of the OEM hose by twice the thickness of whatever it is you stick in there. Sch 40 PVC is thick stuff, and if you are using that, it's killing flow. DWV is much thinner, but STILL reduces the flow of the OEM hose.
Think about that aspect of installing a traditional BHAF. With a traditional BHAF, you slide the OEM intake hose OVER the outlet of the BHAF. Now, HOW THICK IS THAT OUTLET? The walls of the BHAF outlet are not thin, and that's why it's rigid enough to just clamp the OEM hose directly over it. So the effective airflow diameter of a BHAF is greatly compromised-- EVEN MORE THAN THE STOCK FILTER HOUSING! Note the thinner walls of the stock filter housing outlet relative to the BHAF, because it's made of a harder plastic instead of rubbery plastic whatever stuff
So, fitment is a solved problem provided that the duct tape holds up. Since I have a good 3 inches or more of airspace between the filter and the closest part of the turbo, the tape won't see much heat. I think that this could actually be long-term viable with duct tape!! Crazy, I know. If the duct tape works, then we are in BUSINESS to get this filter out there on the market. It also would flow a lot better, because necking it down to a 4" outlet would probably reduce flow.
Kernel, you asked about dirt. Well, it's way too early to draw conclusions since I've only put on about 3K miles with this thing on. That said, dirt is ZERO on the intake hose, turbo blades and all that. Zip, nada--it's as clean as I remember the stock setup being. It's probably cleaner in reality, as the stock filter has the leaky clamshell panel design.
One last thing in this update: TURBO WHINE. Before I fixed the ductwork and my crappy installation, turbo whine was pretty reasonable-- about what a regular BHAF would do.
Now, it's like an F-16 is following me at point-blank range! I can almost hear my warning bipper from his missile lock!! :-laf I caught myself "switching to guns" a couple times-- he was close!
Turbo whine is sufficient to be heard over the HVAC when set on Max A/C on the highest fan level. My HVAC on max A/C is loud; the whine is louder.
I have to admit, the crazy whine sounds cool around town, but is VERY annoying on the hwy. I'm not sure if this is because I cut a Scotty-style cowl hole or not. It's probably a big part of it. I'd say that anyone else who wants to run this filter with a cowl hole should consider the silencer ring and/or TAG. Whine is very strong and gets really bad-- or good, depending on whether you like your ears to work later in life.
I'm not sure what additional benefit, if any, my little cowl hole provides, so I may just plug it back up. I may also rig up a dam of some kind like others have done to reduce whine.
Thus far, I am LOVING this filter, and Donaldson is going to have to hunt me down like a rabid animal and pry it from my dead fingers to get it back.
Justin