What was found
AIRCRAFT DECLARED AN EMERGENCY AND PERFORMED AND AIR TURN BACK TO BOS. AIRCRAFT FLIGHT CONTROLS STIFF AND DIFFICULT TO TURN. AIRCRAFT WOULD NOT MAINTAIN LATERAL COURSE WITH AUTO PILOT ON. AUTO PILOT FAILED. NO ABNORMAL INDICATIONS ON ANY SYSTEMS PAGE. BOTH CAPTAIN AND FIRST OFFICER CONTROLS EFFECTED; REF ITEM #2 OF LOG PAGE 3885671 (REMOVED AND REPLACED THE AILERON INBD PCU IAW AMM 27-12-01. OPS CHECK OK. ) AND ITEM #2 OF LOG PAGE 3885672 (C/W THE RIGGING OF THE AILERON PCU PER AMM 27-12-01. C/W THE RIGGING OF THE AILERON POSITION SENSOR PER AMM 27-13-02. RIGGING AND OPS CHECK SATIFACTORY.) FOR CORRECTIVE ACTIONS.