[speeddemon11383]

Pull off your intake tubing and check your back turbo. That should tell you what is going on. If the turbo spins freely it's not the turbo. You should be able to reach the turbine without removing much other that the tubing. While you're at it remove the front turbo pipe too, and compare. Coming from someone who has blown 3 back 15g's it seems to me the back turbo is prone to failure before the front.
When my back turbo blew there was a bigger smoke show than a top fuel dragster doing a burn out. (Not enough time for story LOL) after that no boost, white smoke but no grinding because the exhaust turbine was in my exhaust tip, which is prob. not your case.