The idle air control valve is probably gummed up with oil vapors from the turbo. You'll need to remove the IAC and give the valve device a good shot of spray brake/carb cleaner. If your rubber intake tubes are oily the compressor bypass valve is bad also and will contribute to the problem. You can check the IAC by connecting 12 volts to the center pin and grounding the outer pins one at a time. The valve should quickly flip back and forth.