The car had the shielded K&N filter on it when I bought it and the hole was there already.
I modified a Subaru WRX MAF to Pod filter adapter I got from Supercheap for about $10 by cutting grooves into it for a seams on the firewall itself. I then bolted it to the firewall and connected the Filter to the MAF adapter with silicone pipe.
No vibrations and all the cold air goodness.
