Hello together! Have written a post here some time ago, but do not find it again, therefore here again. I hope that someone can help me here! My S4 with AAN machine does the following: It starts flawlessly and turns in the stand also impeccable high. As soon as I put it under load and wants to speed it up, it sounds as if it blows the air from the turbocharger into the engine room. No hissing, but a rather blazing sound from the front right. The vehicle has an automatic transmission. Can therefore not speed it up ,there is nothing ….. nothing at all. However, if I move the accelerator very little , it accelerates (although slow but it drives ) I have exchanged after reading the computer : Lambda probe, all pressure fumes and pop-off valve . I immediately replaced the pop-off with a piston pop-off valve . Now I wonder where the air goes out or what else could be ….. I hope , me can here someone help , the workshop really doesn’t know any more , anyway until now and the car is now for more than three weeks time again in the workshop . I thank you for your help in advance !!! Greeting Duke