2006 saab 95 2.3t i have replaced the direct ignition twice in the past month. the spark plugs. cleaned the fuel injectors.new air filter. cleaned the mass air flow censor. the car still misfires. usually only cylinder 4. it only happens when i try and take off quick, or when im cruising at 70 and try and down shift to a lower gear, and gas it. the car misfires and loses power. if i drive like an old woman, the car runs fine. any ideas?