Have 04 Lexus 330..190k miles..very bad vibration While braking but not always..changed rotors and still sometimes vibrates hard when braking?

 

Shaking can be caused by a few root causes:

Warped rotors
Loose caliper bolts
Suspension
ABS issues

 

Did you replace your pads? If so, did you check the caliper slide pins? I had 2 seized on my rx400h and it caused awful shaking when braking.

 

check wheel bearings

 

Could be seized calipers.

If you recently replaced the brakes with new pads and rotors, it could also be that the new pads weren't burnished before they were installed and had deposits and imperfections on the surface.

If the vibrations and shaking occurs at all speeds, it may be driveshaft issue.