What is a BHAF?
Well... ... ... Since no one has jumped in yet

, I'll try to help you out a little. I don't have a
BHAF 
but I've read about it. Hopefully someone with direct experience will help you out.
Just to get you started,
BHAF just stands for
Big
Honking
Air
Filter. It's just an aconynm someone cleverly made up I guess. They are very large cylindrical paper filters that will fit onto your current "filter to Turbo" air input hose in place of your current stock airbox and filter. Kinda looks like something you'd find on a big rig. I never priced them but I believe they cost about $35

and they cannot be re-used like the
AFE filters :{ .
NAPA and Fleetguard have them... others can give you PN's. They need to be sized to fit the turbo hose and fit under the hood (barely). There are heat shields available and socks to help protect them.
I don't know what the flow of the
BHAF is compared to the
AFE, but apparently they flow better and a lot of guys here like them better and they are cheaper

. You'll hear good and bad about both... kinda stirs things up when you bring it up :-{} .
Here is a link to a recent thread posted last month that has pics:
https://www.turbodieselregister.com/forums/showthread.php?t=120212&highlight=bhaf
If you search on "
BHAF" you will find hours of reading enjoyment.
Hope that helps some. Those with PN's can post them for you or look in the thread above that has the pics and PN's.
I got the
AFE Stage I and am going to try that cause it has a niffty sticker :-laf , and it does come with the heat shieild Oo. too . Seriously tho, there are pro's and con's for both.
Good luck,
Dave