Brakes & Front End Hopping

Not quite sure how to describe it, but when braking, the front end seems to want to hop and stutter. It's really annoying. I have an 01 Silverado Z71...35K miles...only suspension modification is torsion bar adjustment to level; new 18" wheels and Hancook tires.

Before the tires warm up, it pulls heavily to the left under braking. But once the tires are warm it stops pulling and just has the consistent hopping and stutter under braking. What a pain :banghead:

Have thought about going to larger rotors and calipers... replacing the front rotors with higher grade and better pads... etc.

Any thoughts would be greatly appreciated.

Thanks