What was found
INSPECTION TYPE:N/A, IN CRUISE AFTER AN ATC REQUIRED SPEED REDUCTION, B AUTOPILOT ABRUPTLY PITCHED A/C NOSE UP (ADDITIONAL 2.5 - 3 DEGREES. F/O PUSHED OVER BUT COULD NOT PREVENT AN ALTITUDE DEVIATION OF 300 FT NEITHER A/P OR ALTITUDE HOLD DISENGAGED AUTOMATICALLY. SUBSEQUENT A A/P OPS NORMAL. B A/P DISCREPANCY RECURRED WHEN RE-ENGAGED. *S/D* REMOVED AND REPLACED B SYSTEM PITCH COMPUTER PER MM 22-12-01, PERFORMED OPS CHECK AND AUTOPILOT CHECKS NORMAL.