my car backfires also, kinda annoying,
the possible problems are
1. bad spark plugs but they are iridium so most likely not
2. bad tank of gas but happens with more than 1 fill up
3. bad spark plug wires but the 7th gen have Electronic ignition so i cant be that.
simple as this: Gas, force air out--- you shift--- air in and then out again when you gas again...!
5. anybody else want to add to the list to what the problem might be please do so we can possibly find the cause and fix the problem.