Help! I have a (well it was great!) S4 twin-turbo that has just covered 83000 miles (i've had it since 42k and turbos were replaced under wty at around 15k for some reason). Its been mildly remapped by MRC Tuning (great guys!) nearly 2 years ago (60k) and has run really well since. Just had it MOT'd today and did that foolish thing of thinking I must sell her really (reluctantly!) and, then, on an enthusiastic take off tonight, heard a slight "pop", which coincided with power loss, noticed a small puff of smoke out the back and that was that, NO TURBO - or at least, no boost. The car drove ok after that, though clearly not as swiftly as it had (!) and I stopped shortly and checked - all running fine at idle, then noticed a slight mechanical rattle like a loose baffle or heatshield (comes and goes depending on throttle). I drove the car gently home and checked it over and the sound is coming from the back of the engine, down around the downpipes, but I cant exactly find where or what..! Have I popped the turbos or (PLEASE!) have I popped something simple like a diverter valve or summat - has anyone else had the same and what do i do next?! btw - there's no evidence of rough running or any smoke at all on driving.