My partners diesel A Class cuts out intermittently,but usually when accelerating.I took it to a Mercedes garage who replaced the fuel filter and pipes attached.This did not cure the problem as air bubbles could still be seen.They now want to remove the manifold at a cost of £400 to access some fuel pipes to see if there is a leek,is this correct.There is a slight smell of diesl fumes from the front of the car.Any ideas please.