on a smooth straight road above 100 kph my c5 steering develops a slight out of balance effect. i have had the balance and alignment checked and found to be ok. could it be that the power steering is "hunting" to find dead centre? if so i would thing this could be adjusted out but the dealer says" this happens with these cars sometimes". years ago i had a nissan 300c which did the same thing. the problem does not exist if there is any loading on the steering, for example when the road is a bit undulating, the surface is a bit uneven or when going around a curve. any suggestions?