As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AS WE REDUCED POWER TO MAKE DESCENT INTO MEM WE AGAIN GOT THE PLASTIC ODOR SMELL IN THE CABIN AND IN THE COCKPIT. PERFORMED HIGH POWER ENGINE RUN ON LT/RT ENGINE. ISOLATED ALL BLEED SOURCES, ENG APU, RAN PACKS FULL HOT AND COLD SEVERAL TIMES. NO ODORS OF ANY KIND NOTED. ENG RUNS OP/C GOOD. IAW 71-00-00 76-10-00 PACK OP/C IAW AMM 21-50-00. REF AML 2228392 FOR WORK SCOPE PACKAGE PERFORMED.