Other than gelatin what makes gummy bears chewy?
From a package: 


  corn syrup, sucrose, gelatin, citric acid, apple juice concentrate, sodium citrate,
      coconut oil, natural and artificial flavors, carnauba wax, red 40, yellow 5, blue 1


Likely the sugar types and their ratio is important. pH (citrate) shouldn't make a lot of difference unless you're using something weird instead of apple juice. Carnauba wax is likely a mold release agent, which leaves coconut oil as the most mysterious ingredient. I wouldn't bet on it affecting chewiness much, but these dense gel recipes can be pretty sensitive to minor ingredients.