Of note, when I went to a BHAF, I also purchased a 4" PVC coupler to reinforce the BHAF's "flange" that the intake tube connects to. Made for a nice tight union between the two that did not fail.
I did this because I had read on here of BHAF users that had the BHAF come loose from the intake tube, allowing unfiltered air into the engine. No biggie, just a precaution.
Duane