My 87 D150 truck is having a braking issue. After the truck sits for a few days, occasionally when I pull it out of the driveway the first few times I hit the brakes they are EXTREMELY touchy, usually locking up the driver side front wheel. After making a few stops, the brakes go back to "normal", but it does pull slightly to the driver side under harder braking....Any idea what this would be from? I got this truck last fall, and since them I have been fixing a LONG list of things that the previous owner rigged or fixed wrong....this probably being another.

Any help would be appreciated.