4th Time's the Charm
 

Since delivery, my 2015 Hond Fit EX-L would "pop" about 30 seconds into driving (in "drive" forward motion, not idle) under engine load only once every drive cycle. The pop sounded like backfire, from the exhaust.
So, after 4 services at the dealership. First time, duplicated and ran through computer tests, unable to determine source of cause. Second time, removed the fuel pump and reinstalled, nothing changed. Third time, they replaced the fuel injectors, nothing changed. Fourth time, they replaced the cyclinder head, issue resolved. Expensive service, thank goodness for warranty, but the pop is gone, and all is well.
Just wanted to inform any others that may have an identical issue.

Hasn't happened to me, but it's a good thing to keep in mind. Thank you!