[Three_thirty_I]

How often is the oil changed? What's the car's mileage? Have you inspected the Eccentric Shaft sensor's plug for oil leaks? One thing that could also play a part although you have already replaced one of the Vanos solenoids is the Check valve filters that can get all clogged up - they filter and feed the oil to the solenoids and Vanos etc.

Software update is also something to do, but I tend to think that unless the fuel has changed a lot, it shouldn't make too much difference unless it been suffering with this problem for ages.

Hope you are able to find the cause of this.