Ill try to sum this up as quick as possible
'04 f150 screw w/ 5.4 - 185k

Bought pickup a year ago and it had a misfire (no codes). I figured it was the plugs but really dreaded changing them so I drove it for roughly 8 months (it would buck when under load in OD), maybe 4k miles, on the bad plugs. Finally changed the plugs and all 8 broke even tho they were not original (no anti-sieze whatsoever).
Pickup drives smooth and idles better, however now instead of bucking under load there is a droaning low growl noise. I believe it coming from the engine compartment but im not totally sure. Well this morning it my CEL came on for the first time ever. P0430...im sure I smoked the CAT's. Is that the sure fire issue or could it be a sensor of some sort (MAF, o2)?
Which CAT would be bad if that's the code? Fronts or rears? Rights or lefts?

Yes ive looked all over for an answer but cant seem to find anything with my scenario. Sorry and Thanks in advance.

 

P0430 is bank 2 cat efficiency - that's driver's side. Could be either front or rear.