I'd have said engine mounts too.
Get under the car and give the exhaust a good shake.
If it has been badly fitted or one of the rubber hangers is broken or the wrong type it will hit the floor.
Check the driveshafts and the suspension linkages and bushes.
Does the gearstick jump about?
Take it to a different Renault dealer- I still think it's a failing engine mount!!
Brian.J.
August 2008