Random rich fuel, misfires, and no codes

2012 Mazdaspeed 3
52,000 miles
no mods
no tuning
I've replaced the HPFP, both o2 sensors, spark plugs, fuel filter, air filter, and front cat. The symptoms have not changed.
I bought this car about 6 months ago from an elderly woman whose husband (this was his car) just died.
The car will run amazing, everything is crisp and the car is super fun to drive. However, randomly, every couple days, it will just LOSE ITS MIND, and run stupid rich. Black smoke coming out the back, backfiring, and bucking like I'm trying to ride a bull. I can usually drive it home by putting it in the highest gear possible and just living with the bucking and jerking. But, eventually it'll just fix itself and drive PERFECT out of nowhere. I've hooked up a scanner and when it is throwing a tantrum the fuel pressure will be around 500 at idle and 1200 if I give it any throttle.
It throws no codes, no check engine light, no pending codes, NOTHING.
I replaced the front cat because both cats were melted and hollow from before I bought the car,
I have no idea what the hell is going on.

Please, any help would be like nectar from the gods at this point,
Thanks!!

 

I think i got same problem, cylinder 4 has some oil on piston