Clutch or Syncro's
 

95 Z28 6 speed. My car use to grind when i chaged gears. The grinding is still there and now it pops out of gears (1st, 3rd and 5th)

Anyone know what can be the problem?

If its grinding going into gears it more then likely the syncros

^It's not grinding going into gears, it's grinding when i shift at high rpm. For example, if i shift around 3000 or 4000 rpm then it grinds. If i shift at 2000 rpm it doesn't. It just pops out of gears.