As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT HEARD SEVERAL RAPID POPS LASTING 3-4 SECONDS, TWO EVENTS SPACED 10-15 SEC APART. LEFT ENG N1, ITT, N2 FLUCTUATED, ALSO EXPERIENCED SOME AIRFRAME VIBRATIONS. DECLARED EMERGENCY AND ACCOMPLISHED AIR TURNBACK TO VNY. ITEM IS UNDER INVESTIGATION.