Help! Knocking noise coming from gearbox.ish
 

Hey all. Firstly, poor title and I apologise .. right I have a 06 wrx and I fairly recently had a 6speed conversion done ( by a specialist, no names just in case) and it was all done properly so I believe. But recently the clutch is now super high bite point and when it does engage its either on or off . So the noise I get it when it engages with a knock but its hard to tell if its the clutch area or maybe rear diff?! I paid for a new clutch in the conversion so I hope its not that , or maybe a dodgy install? I dont know. But the cars a pig to drive and real hard to make a nice gear change due to the mental high clutch point and the bang I get a if not not as smooth as.butter with it!. Ill be getting the box and diff oil changed soon to but wondering to ask for the box to he dropped out and the local guys to have a look ( triton motorsport ) any help, tips or advise welcome! Thanks

Anyone got any ideas?!