Problem with '89 Ford Probe GT Turbo

I just took my '89 Probe to the shop today. There was smoke rolling from under the hood and it smelled like anti-freeze. A few motor-heads looked at it and said it could be the thermostat, the water pump, or it needed to be flushed. I took it in today and they replaced the thermostat (that was part of the problem). After driving it for a little while, the smoke started again but it smelled different - more like something was burning. It's coming from underneath the turbo . . . what could it be?????