ok i posted about a week ago saying the car sometimes switches off at junctions, well since then i took it to renault and they said it was the spark plug (again) and they changed it for new ones. well since i had it back i noticed that theres not much change (hasnt swtiched off at junctions YET) however i feel a big power loss, especially when accerlating and on the whole the car just doesnt feel right. can anyone help?