As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH POWER APPLIED HAD A SMELL LIKE BURNING RUBBER. DISSIPATED WITH POWER BACK, NO INDICATIONS. RAN BOTH ENGINES TO T/O POWER WITH PACKS ON, NO SMELL. CHECKED AIR MIX DISTRIBUTION PLENUM IN FWD BAG BIN, NO CRACKS OR LEAKS. REPLACED RIGHT AND LEFT WATER SEPARATOR BAGS. LEAK CHECK OK.