/6 tanks when in gear

Not sure if this is strictly and engine problem but it's my fault for buying a Chinese carb.
So in any gear besides Park or Neutral the rpms drop like a stone and the whole car shakes like an earthquake.
Once you get gas on it, it runs about as smooth as a car that's been sitting for 20 years can but it has enough power to burn up the parking brakes because i forgot they were still pulled:BangHead:.

I know automatics are supposed to drop when in gear, but how much is too much?