an anyone help i have a vectra sri 150 and i did the head gasket last year after buying the car with head damage(timming chains snapped ) the head went away and had the damaged valves and valve guides done the car ran fine until last week ,when pulling away from junctions theres a cloud of smoke whitish/grey but when driving on the road and you drop a gear and put your foot down theres no smoke? my freind said its the valve stem seals and prob worn valve guides what do you think . also will i have to change the timming chain adjusters they are nearly a year old thanx paul