Please help - Car making a misfire noise

[CMF_MissM]

When my car comes off the reves it seems to make a "popping" noise like it's backfiring. It has only started doing this in the last month or so but apprently it is normal for this car . Anyone else heard of their car doing this?

The garage have told me this is normal and that there is nothing wrong with my car but I think there is something wrong. Can anyone advise?
thanks