Slow acceleration, rough idling, #2 cyl misfiring, Happened after using seafoam Options

[Cutrara]

I recently purchased a 96 st and thought I would run seafoam through it... took it up through the brake booster line. Of course it smoked like crazy, but was still smoking a few days later with a CEL on.

Took it to autozone, code P0302 #2 cylinder misfire. the plugs looked like they had a lot of grayish yellow deposits on them, #2 was significantly worse, so i replaced all the plugs with autolite double platinum and the car still has trouble accelerating... if i take off from a light it feels like i'm in third.

i also tried disconnecting the battery and resetting the afr (pull ecu hazard and efi fuses, idle for 10 mins) and still having problems. also checked all the plug wires, they look ok... I havent yet pulled off the dizzy cap.

Could it be the O2 sensor? but it didn't throw an O2 sensor code?? I suppose I could throw in the O2 sensors from my other celica, but my parts car is a 94 st obd-i and has a 1 wire front O2 sensor and my dd is a 96 st obd-ii cali-spec and has a 2 wire front O2 sensor. so idk if this will work. Haven't looked under the cars yet to take a look at the post cat sensors... if there are any?

I'm worried about my cat too cause of the misfiring. Any ideas?

[Bitter]

compression is fine, that cylinder is fine mechanically. there is some fuel getting to the cylinder because the plug is blackening but you're not getting good or complete combustion for whatever reason, poor spark or a bad fuel injector. ohms check the injectors and make sure they all read about the same resistance. mechanically the injector can be clogged or stuck open and either of those will admit fuel but cause rough running. as for spark a cracked cap will cause this as well. from how the plug looks you probably have either a weak spark or too much fuel. its pretty dark which is rich.