What was found
EXTREME SEWER SMELL ON TAXI OUT OF LGA AND ORD ...BOTH FLTS...D ISAPPATE AFTER TAKEOFF.AFT GALLE DEBRIEFED FLIGHT CREW, SPECIFIED SMELL WAS DURING TIME ON APU BLEED, RAN APU AND BLEED AIR MULTIPLE TIMES, NO SMELL NOTED. PER CREW LAV E WAS WORST SMELL, REMOVED AND INSTALLED LAV E TOILET SHROUD IN REF AMM 38-32-01, NO FOREIGN MATERIAL NOTED AT THIS TIME