I would say since you've replaced the plugs already to test the ign. coils. You can swap them around but you have 3 that sound like they might be gone. So swap side to side and see. Another way is, with the car running, gently lift the coil off the spark plug and listen for arcing, if there isn't any, then that coil isn't working. If you were closer I could have lent a hand.
Let us know
www.enthusiastauto.caNeed a car???
--'00 BMW ///M5 .:Jet BLK/BLK:.Individual-Style 65 Wheels; 9.5" Square Set up;275 Tires;Spacers;Black Kidneys;Muffler Delete; 3.5" Dual Tips; Beast Power; "Dinan" Ducts; E60 SSK; BC Coils
--'07 BMW M5/6.:Indianapolis Red
'88 BMW 635CSi
'81 MB 500 SEC Koenig