Mechanics clueless about engine misfire

Three mechanics so far and the problem is not corrected.

2003 Hyundai Elantra

Car jerks back and forth, gas pedal is pushed to floor and it won't accelerate then it recovers; does this constantly

po303 cylinder misfire number 3
po304 cylinder misfire number 4
po300 cylinder misfire random

Spark plugs, wires replaced -- problem still exists

2 coils replaced- helped a little but not much

seafoam put in engine - problem still exists

after this, still have the po303 and po304 codes and the car still shakes and has trouble accelerating