Random misfire still in 1997 malibu?

before i noticed my intake was bad as it was i was driving home i had put coolant in it rand out and after i went to a gas station the car started running funny and giving me a random misfire so i got it fixed and my car is still giving me random misfire when rpm goes past 800 and idles fine for the most part but be Driving it misses what is wrong with it 97 malibu 3100 sfi vin number m