With the older A-bodies, there was a huge difference between Canadian-built and US-built models. This went away after the 80's. With the A-body hub, its retard-simple. What it sounds like to me (and my experience with A-bodies) is either the wrong pads were installed or right pads backwards (which can happen with these calipers), or the ABS actuator is on its way out. Now, the great thing about GM's is you can unplug the leads off the accumulators on the side of the master cylinder. You'll see the leads (orange and black wires or orange and gray wires- model year differences). Unplug that, the ABS won't work, traction control goes buh-bye and there is now an ABS warning light lit on the dash which is fine because its already lit anyway.
Now, does the front end growl, shake (other than the tires) or hum real hard?
also, another thing is check to make sure the hub nut has not backed off. I have seen that happen before. The three bolts that hold the bearing hub to the knuckle will back out and cause trouble if they aren't torqued correctly. Ditto with the big nut on the axle. Your rotor will shuck all over the place. Oh yeah, almost forgot, with the mileage that car has, i am sure the hubs have been replaced at least once... i wonder if they were installed in the knuckle correctly?
also, the light switches on these cars overheat and fail all the time. Especially on the Regals which is just an upscale Century. If it's got power windows, order driver side switches now...