Seen this particular issue with the PVC units previously.
By the way, they look great in mid-heat candy red or purple
Remove the 3 bungs with a wrench, if they crack the pvc when doing this then there is no big loss as you wanted to replace it anyway. Make sure you wrap them with thick Teflon tape and re-install. That pvc part can be found at the larger home improvement stores and plumbing supply houses on the cheap if you stick with it.
Now that I have used the newer silicone boots, I can appreciate how well they seal compared to the standard black rubber found on these. O'Reily has a good selection as well as Pep Boys - that way you eliminate that part as a leak as well, short of the filter itself from consideration. Use the double-metal strap sleeves if available for the ends of the silicone boots (ala Turbo Look).
I look through my stash for a 1.7 air box just in case and contact you via PM if I find one...
Dave