He put the car up on the lift, and checked the dimensions of the wheel cylinders (which the shop had ordered) - they appear the same on the outside, but the insides were different diameters! One side is getting more drag that the other, which accounts for the pulling.
New cylinders have arrived, and Tuesday I drop the car off for the installation. But, here's the question:
After the car warms, I still get a screech on a hard stop. Could that be explained by the difference in drag? Or do I still have a (different) problem?