It is normal for an engine to drop a few rpms before it recovers if you cut the throttle. This is because the engine is hot after running full throttle and cooling down on idle. If it causes your engine to quit it might be running too hot because of an air circulation issue or too lean HS setting. There's no need to try different settings, simply (here we go again):

- run engine hot
- close LS 1/16 at a time until engine starts surging if you open the throttle, then open 1/8
- adjust HS for max rpm, open HS 1/16 or 200rpm drop

Repeat this procedure at least once. If you still have issues, check your air flow.