99 slk 230

I have a 99 slk 230 with 131k , I just replaced the spark plugs an wires an ignition coils. Did an oil change . And I still have no gitty up , it has no launch  .drives slow until I get up to 25 mph an then I have to feather it or itll start misfire. I shut it off an it'll stop the misfire . Idk what to look for