smoking and loss of power at boost

I have a 93 vr-4 with 42.000 mi and no upgrades, when I hit about 4,500 to 5,000 rpm it falls on it's face, when I let off the gas it picks back up again. It also has some white smoke (or blueish white) hard to tell, coming out the back. it has been said this happens when the turbos are going out. is this true-and if so is there a way to test for sure. could there be another cause for these symtoms???????????

thanks for any help.