In a way that could be good news! The heat hopefully just burnt the electrodes and flew out the exhaust (Or mangled up with the rest of your CATs)
Get an engine scope in there to see whats going on.
What spark plugs do you use? low 30s gap is still too wide of a gap, 28 is the best gap I use with no drivability problems whatsoever. Also stick with the NGK LFR7AIX. I've tried and tested them on countless cars and they do a good job!