'88 300E Suspension Woes

[Rage0582]

Hoping someone can help on this issue, I have a 1988 300E and it's having some front suspension issues. So, to the problem...the car runs and drives fine at low speeds, but at highway speed, the car's front end begins to sway left and right. I'm not sure what the issue is. I know that my passenger's side ball joint needs to be replaced soon, and that may be the problem. However, I have pushed down on the hood on both sides of the car and the strut on the passenger's side makes a hissing noise on the rebound. I have also noticed a squeaking at low speeds going over bumps. I checked my front and rear swaybars and the bushings look fine. My other 300E had the low speed squeak issues from the front and I replaced the swaybar bushings and it went away. I never had issues like these with my other 300 and any help/advise would be greatly appreciated!!!

Thanks,

Roy