I have a 200 a4 1.8 turbo quattro 5 speed, and when I am accelerating in any gear the car will stop at 5000 RPM. It only does this when I have boost built up, the car will pull strong until 5000 RPM with about 11 lbs of boost then when it gets to 5K i lose all of my boost pressure. The car is throwing a couple of codes. The codes are bank 1 sensor 1 (i guess this is an oxygen sensor?), and it is also saying something about tyhe car is running to lean. Any ideas would be helpful. Thanks in advance for the help.

 

Check for vacuum leaks. Have the codes read and post them.