I have a 2000 a4 1.8t 5 speed quattro and when i punch it to the floor there is a greyish/black smoke that comes out the exhaust can someone help me figure out what this is.

 

that's quite normal your putting a demand on the engine, blue smoke you have to worry about

 

so the smoke i dont have to worry about its not burning anything like oil

 

If you're burning oil, you'll usually see a lot of black smoke out of your exhaust

 

oil burner = blue smoke
white = water/coolant but with the catalyst this is normal
gray/black is either you are booting it or your not but if not then the fuel/air mix is out of calibration.

I guess your booting so its normal