Without hearing it, it would be hard to tell. My guess is it is probably rich. You would need to turn the idle needle valve in about a 1/16 turn at a time. This is with the restrictor off in this case. I have had some engines that could not be adjusted to transition smoothly with the restrictor. There was a hesitation before it throttle up. We left it like that until there was more run in time on the engine. In some cases a students plane would get better. But in all cases, after lots of run in time (usually about 30 flights or so) we removed the restrictors. If you throttle up and it just dies (without the hesitation), that would indicate to me the idle mixture is lean. I think that is doubtfull since they ship these things running rich, but it's possible. Better to have someone help you with the engine at the local flying field. They will be able to hear what is happening better than me just speculating. This of cource is, just my opinion.