Sounds like carbs.If they are clean then ajust the fuel screw 1/4 turn till you get best results.Ive been messing with mine .First I but reeds in had to turn in ,then put tempa flow on had to turn out.I like to do one thing at a time so I know what did what .I had that bog each change & tuned it till it was nice & responsive each time.Second time I went the wrong way couple clicks before going back the other way it started to pop.Some say they can tell if its rich or lean but it sounds the same to me.All I can do is guess if it dont work go the other way.When the twin is good youll know it