Looking for some ideas on this one. Had to have the regal towed back home this morning. With no warning, started running rough and was way down on power. Getting HEAVY fuel smell out exhaust, and these codes:

p0128 coolant thermostat
p0300 Random/multiple misfire
p0420 Catalyst below efficiency, bank 1

I believe the 0420 has been there since I installed the ZZP DP several years ago. The raw fuel smell is very strong, like straight fuel out the tailpipe. Any ideas where to check first? I'd appreciate any help.