As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FLT 4223 - ON CLIMB-OUT, THE CREW EXPERIENCED A LEFT ENGINE DELTA T-SHIFT OF 60 DEGREES. AIRCRAFT RETURNED TO BOS AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND PAPER IN ENGINE INTAKE. REMOVED PAPER AND ENGINE GROUND RAN WITH ALL SYSTEMS CHECKING GOOD. AIRCRAFT RETURNED TO SERVICE. (X)