I have a 1999 audi a4 quattro and when I accelerate, there is a fluddering noise coming from the driver side of the engine, so if your facing my car it would be on your right. It only happens when I first start driving, once the car heats up, the noise goes away. This only happens when I hit the gas while I am driving. If i am in park and hit the gas, the noise does not happen. Also while Im driving and I do not hit the peddle, the noise does not happen. What do you think it is? Thank you.

 

I would start with a boost leak check.