Okay, I put the filter back, and after the initial "rough idle," everything seems back to normal.
Guess it was dumb of me to think I could just take out the 2nd filter... I shoulda known it wouldn't seal properly.
I highly doubt this, but do you guys think I've done any permanent damage? Everything seems okay, except for the CEL, which I will be resetting after work.
Thanks for all yer help!