I just picked up a K&N drop-in today, and was looking for an easy way to get the air from the grill up to the now open hole where the snorkel was. I came up with a decent setup. I didn't want to cut or remove the flap, as I would like to be able to reverse the process if need be (doubt I ever will).
I cut a piece of clear plastic from packaging for something, about 8" by 4", and shimmied it between the bumper cover and the plastic reinforcement under it. I than taped it to the plastic piece that holds the rubber flap. This should hold the flap down in front of the drivers side grill, allowing air into the intake opening.
Gone (But not forgotten) - 2013 HB MTX, Tux Black w/ Black Pack - Steeda RSB, Snorkel DLT, K&N Drop in, E-Focus RMM, Redline Tuning Hood Struts, Custom Al. Skid-plate, 180 Stat, Tune by Tom @ Focus-Power
Current - 2000 Mazda MX5