Sounds from the gas fire

[Listengold]

Recently we had a new boiler and all the gas pipes had to be replaced.
Old pipes were narrower.
Ever since when the fire is on it makes a fluttering sound.
Pilot light etc have been cleaned. Gas engineer said it will stop soon
yet it's nearly 2 weeks now.
Any suggestions on how to stop this sound

Bump

My gas fire makes a tapping sound until it warms up, sound stops after a few minutes, looks lovely by the way.

@user1471505356 they do look good. But this sound was all the time.
Tried again to clean around the pilot light a minute speck fell off and fingers crossed
the fluttering sound has stopped.