Perhaps you've already checked out the pads & rotors on your rig, but the rotors could be trashed. A quick visual inspection through the wheels won't show where the real damage is on mine - the backs of both of my front rotors are destroyed. I'm guessing that's why my pedal feels spongy.
I'm thinking of trying a set of these:
http://cgi.ebay.com/ebaymotors/Magnu...70244204QQrdZ1
I know the classic Jeep guys (earlycj5.com) had some good reasons for drilling their drums, but is there really any off-track advantage to drilled rotors?