Hi everyone, I'm new here so excuse me if this is posted in the wrong place. So I bought a 2006 A4 Avant S-Line 2.0TDI 140 in November last year. When I bought the car it had been sitting for a short while (2 months or so) Since then, it has been producing more and more black smoke, but the turbo range has stayed pretty much the same from what I can remember. The car comes onto boost at about 2200RPM, and then the smoke will go away, but below that there are plumes of black smoke coming out of the exhaust. At first I dismissed it as normal due to the engine not having enough air from the turbo at these low RPMs to burn the fuel but it's got really bad now. At the moment it is so bad that after about 3 days or so the whole left rear of the car will be significantly blackened by the amount of diesel smoke that comes out of the exhaust. I know the TDI140 engines didn't have a DPF but this is excessive for any stock engine DPF or not. Currently when cold the car feels like it doesn't have a lot of power, for example it's tricky to do a hill start on a steep hill without almost stalling the engine (manual trans). It's not like I'm doing short trips for carbon to build up either, I have done 7 thousand miles in the car now, and just last night I took it 500 miles to West Sussex and back. Most of my driving is motorway, but I do have a spirited driving style on the smaller roads, so I don't think anything could've built up in the engine due to not driving it hard enough etc. The car has a CEL on (code P21o8 'Throttle actuator control module performance) so this could be a related fault. Has anyone got any ideas as to what the problem may be?