What was found
AFTER TAKEOFF FO'S EFIS WENT TO SKELETON MODE ON BOTH TUBES, ATT, PITCH, ROLL AND HDG FLAGS APPEARED, QRH COMPLETED -XSIDE DATA SELECTED. AIRCRAFT RETURNED TO MSP. MAINTENANCE COULD NOT DUPLICATE ON GROUND. REPLACED NR 2 AHRS AS PRECAUTIONARY MEASURE. SYSTEMS OPS CHECK GOOD IAW SF 340 MM.