Problems with 2010 Infiniti M35 VEHICLE SPEED CONTROL

Driving with cruise control on, 70mph zone, slight downhill speed of 72mph. new rear tires, very good condition front tires, 1 day old 4 wheel alignment, concrete highway surface in sunny dry conditions, approximate outside temp 65. vehicle and steering wheel jerked to the right with steering wheel displacing approximately 30-45 degrees from center to the right, followed by a jerk and displacement to the left of approximately 30-45 degrees to the left and repeated to the right and left again... car was uncontrollable... reduced speed, killed cruise control, lightly applied brakes. car became more controllable as speed was reduced. major auto repair location and ase certified mechanics diagnosed as problem with rack and pinion, possibly "a stuck valve" causing excessive steering inputs to be allowed at higher speeds than normal. *js

When car is slowing down, it will jump wildly with the rpm's and shift into different gears. car could hit another car or person if the brake is not held firmly. cannot get the local dealer or corp. to acknowledge the problem or fix it. the car is still under warranty. the problem is getting worse but the dealer says to drive it until there is a hard failure. i am concerned the car will jump and hit something or someone. the dealer says there could be a computer problem but they are not sure and do not want to eat the cost of a computer if that is not the problem. i looked this situation up on google and found that this problem is known for this particular model car. it did not do this before until about six months ago. *tr