As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DUCT PRESS SPLIT. DURING POWER RUNS USING ASM BLEED MONITORING SOFTWARE, FOUND PRESS OUT OF PRESS RELIEF VLV WAS NORMAL & MATCHED THE LT SIDE AT ALL POWER SETTINGS BUT EICAS INDICATION WAS READING 20-30 PSI LOW COMPARED TO THE ACTUAL PRESS RELIEF VLV OUTPUT PRESS. REPLACE THE RT DUCT PRESS TRANSMITTER M1089.