Improving high speed stability

[garner]

About an hour ago I was chasing a run in Mexico, and about 110 my car was going all over the road. It was tricky trying to keep it in one lane. And when we hit a bump my pedals vibrated(almost like abs) and felt like a loss of steering control.

Everything is stock on the car except ford 07-09 polished bullitts and 235/55/18 yokohama yk580 tires(tires were purchased a couple months ago). There was very light wind(not sure on direction).

Any ideas on what could be causing this? It's pretty sad when my friend's f150 is more stable at 120 than a pony car at 110