annoying problem I need help

[sicones]

well last MONDAY my msd 6a box totally took a shit at he worst possible time on the highway, missed class, had to get towed , brother brought me my tools and fixed it in the parking lot and drove home, wasn’t fun

well here’s some notes and my problem

while the box was dying I drove really slow in the right lane for like a few minutes, the car was misfiring due to losing spark and the check engine light was flashing, I’m guessing this caused me to run really rich, I fixed it in the parking lot with a brand new OEM distributor cap and rotor (don’t ask) and the spark plugs were change 3 days before that (stock NGK), started the car perfectly fine no CEL or nothing


WENSDAY
check engine light P0420 / #67 Catalyst Efficiency Below Threshold, WTF!
now the check engine light has been coming on every other day since then, I clear it every time it comes on with my scanner, I pulled the battery to reset it didn’t help, the cel only seems to come one whenever I am just cruising at around 40-80mph with steady throttle, city driving doesn’t seem to set it off

I really stumped is it possible for the car to just get used to an ignition, its been on there for almost 2 years, now that its off making me run rich, or did running rich for that little amount of time destroy my cat or clogged and 02 sensor, as of right now I haven’t done anything I’m thinking about getting a new 02 sensor but I don’t think that will fix it because the code says the cat is fucked not the sensor HELP!!!