ok I just bought a 03 a4 quattro 1.8t, occasionally when light on the throttle the car will slow down and the rpms drop as if i lifted of throttle. I assume its a throttle by wire issue in the throttle body, no check engine light anyone know what this is.

 

You have to get the fault codes checked, autozone will scan it for free. Then post the fault code here and we can tell you what it is.