BMW Repair: 2002 325i idles rough and has white smoke, internal leaks, coolant level

Question
hi,my name is orlando.my 2002 325i,vin#wbaet37492ng73138,is idling rough and throwing white smoke sometimes.I noticed that when i take the dipstick or the oil fill cap,it sucks air in!the car suddenly runs perfect and then does it again.I already replaced a broken vent hoseunder the intake,i dont know if it might be the ccv valve.PLease help,thanks

Answer
Well idling rough and white smoke, makes me wonder how is the coolant level.Most times white smoke indicates coolant burning.Are there any oil leaks?(ie gaskets,seals)When removing the dipstick or filler cap it affects the engine due to the engine being a closed system(no pcv valve)so it is causing an unmeasured air leak that the computer has to adjust the system for.A cylinder leak down test will help see if there are any internal leaks such as rings,vlaves or head gasket.