the stealership will tell you that they have to tear down the engine and hand clean it. I have had great success with AutoRx in sludged 1.8t's.

The best way to tell is to pull the valve cover and visually inspect the top end.

Below is a post on AZ on how to de-sludge a motor<ul><li><a href="http://audizine.com/forum/showthread.php?t=104440">my sludge technique</a></li></ul>