i have a similar prob in mine
although its when im not hard on the breaks, when i push down on the pedal its not smooth and firm, you can feel little bumps.
im stumped for ideas...
as i have had the disks and pads replaced, although brakes may need to be bled and fluid changed.
what do you guys think?
sorry xr8eater, i may have a similar or the same problem
take it easy
Mark