Good car, Powerful engine but some issues. Review on Chevrolet Optra Magnum

I bought new Optra magnum LS (2.0 TDI) in Oct'2008. I think it is a good car with a very powerful engine along with decent fuel economy. But here is the downside. When the car was delivered to me it had a prob with the wheel alignment. I returned it to the showroom the next day (Nikhil automoble, Navi Mumbai).

They kept the car for 2 days and returned it to me on the 3rd day saying everything was alright. But when I drove the car I found exactly the same problem again (car was pulling to left side). Again I went to the service centre and they apologised to me and again kept the car with them for 1 day. Next day again they called and told me problem was solved. When I took a test drive with their mechanic I found this time the car still had the same problem but now it was pulling to right side.

The mechanic told me it was because of the road on which we were driving was not horizontal and that on good road I will not have any problem. It took their word for it but found that there was still problem. In past 6 to 7 months I have got the wheel alignment done 4 times but the problem is still there. At last the service center told me that it is problem with the model itself and cannot be solved. Also at high speeds (above 150 kmph) a peculiar sound is heard from the front left side of the car which discourages you to speed up further. The steering wheel also feels quite light at high speeds which is not so good with safety point of view.