Engine Sputter?

Greetings all. I've had my '04 Passat GLX for a year and 4 months now.  This past summer, I'd noticed that at an idle, whether in drive (waiting at a light for instance) or park, it would  lightly "kick", like the motor was sputtering.  It's intermittent, the frequency varies (a few times in a row vs just one time with a longer time between the next instance) and doesn't happen while driving.  Not sure if this has anything to do with it, but if it's happening, when I accelerate, it chugs once or twice before moving.  I took it to a dealership.  The tech felt the kick, but didn't have a response given no codes tripped and that it wasn't "noticeable" enough, citing normal operation.  I think otherwise, seeing as it didn't do it the year beforehand.  Any suggestions or anyone experience the same thing?  Thanks much for the help.

  Can't be sure, but it sounds like dirty injectors, most of the time
  they have to be removed and cleaned or replaced, However
  with a little luck and close the left eye while smileing and standing
  on the right foot, you might try some STP injector cleaner, start
  with a full tank of gas and about 2 bottles of injector cleaner, then
  after a refill go with 1 bottle of injector cleaner.
    THAT IS IF IT'S GAS AND NOT DIESEL.

Thanks for the reply.  I stumped the techs also.  He said that if it was an issue, it would have tripped a code.  No codes have come up.  I was always curious of fuel stabilizers and injector cleaners..whether they really work and if they're safe for your vehicle.  I just got some gas (not a FULL tank  but pretty much there).  I'll pick up a couple bottles.  Is this something that would clean right away or would require buying a few  bottles over the near future?
And yes, it's a gas engine.  Thanks again...