Grinding sound in my engine ONLY above 5k RPMs

What could be causing a grinding sound in my engine ONLY above 5k rpms? Also What could be causing my car to idle extremely low while in gear?

A/T and turbo engine

Grinding Sound:
happens whether car is in gear or not
starts at exactly the same rpm every time

Low Idle:
Base idle is about 900-1000
Low idle doesn't change much if base idle gets turned up
idle in gear drops to about 200-400
very slightly rough
Some times the car will die when shifted into D or R; other
times it will not even budge like perfect

Known problems:
car shifts hard some times between gears and when going into
D or R

A while back I had my engine mounts that were bad changed(supposedly), but the car still bangs into gear. I believe my back mount is bad or didn't get changed at all I can't tell, because the engine moves way to much while shifting. It has been doing this for a while and the other 2 problems I am asking about have just come up so I don't know if they are really related or not.