Quick Question...Important

first, owhen my car gets up to about 100km/h my car starts to rattle the steering feels like its going to fall out... what could be casuing this problem? 2nd it feels like my car eats gas when i turn it off when i get home from work then start it in the morning to go to work my tank looks like it has gone down alot, but i get about 400k out of a full tank...?
third when my car is running the engine sounds like somthin is rattling then when the air conditioning is turned on the sound intensifies and sounds like a fast rattleing noise that sounds like somthing is very wrong... what could that be?

First have the tires checked to insure they are in balance if that does not improve the shaking have the CV Joints checked, if no luck you could have bad ball joints. I would bet however that one of the first two will be your problem. Second the guage is probably faulty although these guages are sensative and if you park on an incline at night this could be throwing it off. Finally the clutch could be going bad on the air conditioning compressor. I had a Grand am that made a terrible noise when the compressor engaged but never lost AC nor did I have it fixed. If it is a rattling it could be something that has come loose so check to insure that all bolts and accessories in that area are tight also check any heat shields as they are notorious for vibrating noises.

How old is the car? Just wondering if it's one of these 2000+ grand am's that people on hear are having alot of problems with even though they shouldn't since the car is so new.

only 400k per tank? youch! I get almost 600k on a tank.. and way more when I'm highway driving :)