Good points made as well
Try this before changing anything. Fill the tank halfway and fly it. Go inverted, do some loops, ,climbs, knife-edges and see if the engine sputters and wants to die. If so it's the carb line inside the tank. If it still only does it in a dive and the engine does speed up as mentioned before sputtering then your high end is a bit lean. Open the high speed needle a click and fly it again.
I'm still placing my bet on the clunk and line as I've been there already with it.