What about that warranty you got with the car? Take it back and tell them to fix it -NOW!
Personally, if I had a car with a warranty before I'd try fixing anything myself I'd take it back and get the work done under warranty. That'* your best bet, and they won't hassle around getting to the source because it'* on their budget.

Well it turns out the tires weren't balenced properly so that fixed it pretty much. I think these cars have a slight vibration no matter what- FWD? Because all Bonneys and LSSs have had vibrations that i've driven.

Yeah, I notice a slight one in my car once you....ummmm....get going a little faster than you should

Just don't let you're sister see you've been speeding her old car!