In addition to what ANTHONYD said , I would suggest to drive the car having someone else following you to see if your wheels arent' bouncing like basket balls when you get over pot holes or uneven pavement . If they are , that's a clear case of shocks gone bad . When your wheels don't have constant contact with the road , your car won't have a constant straight course .
http://www.youtube.com/watch?v=xNwAb4Y4BNw&feature=related
http://www.youtube.com/watch?v=k6Y2aexChGs
03 Ford Focus SVT
"If in doubt...flat out". -Colin McRae
http://www.youtube.com/watch?v=k6Y2aexChGs
03 Ford Focus SVT
"If in doubt...flat out". -Colin McRae