running rough !

I have a 1992 Talon TSI. A year ago, It started idling up and down very rapidly on start up. It would also lose power when driving. Since then I have replaced plugs, wires, Coil pack, O2 sensor, fuel filter. Here in the last month it has gotten progressively worse. I still have the idle prob. but now it loses power when I accelerate and Black smoke big time out the exhaust. While its doing this, i'll back off the throttle and it starts to pick up in power a little and the turbo maxes at full boost. It seems to do this during the day when the weather is hot. Doesn't seem to do it in the morning. Any Ideas.

sounds like headgasket to me.

Do a compression test. It doesn't seem like a head gasket to me; there is no evidence of coolant being burned. If I had to guess I'd say you need new piston rings in one or more cylinders.