Afternoon all. So after your help and doing some digging, I'm getting deeper into the problem with my Audi A3 2003 TDI Sport. And I can tell you, it's been very fun learning! The problem with the car: Car goes in to limp mode - Emission Control System light is on - code came up as P0234 (over boost) (another code also came up, see below) - car shudders when idle. The two codes are: 16785/P0401/001025 - Exhaust Gas Recirculation (EGR) System: Insufficient Flow Detected Possible Symptoms Malfunction Indicator Light (MIL) ON Reduced Exhaust Gas Recirculation (EGR) Reduced Power Output/Engine running rough Increased Emissions Possible Causes Exhaust Gas Recirculation (EGR) Flow restricted/clogged Exhaust Gas Recirculation (EGR) Valve stuck closed/leaking/faulty Wiring and/or Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve faulty Exhaust Gas Recirculation (EGR) System faulty Possible Solutions Check/Clean Exhaust Gas Recirculation (EGR) System Check/Replace Exhaust Gas Recirculation (EGR) Valve Check Wiring and/or Connector(s) from/to Exhaust Gas Recirculation (EGR) Valve Special Notes Some TDI-CR engines have a filter for the EGR that can become restricted and cause a "Insufficient Flow" code. With the above, a) is it something to worry about, and if so what could it be and b) could sorting out that problem help sort the following code... 16618/P0234/000564 - Boost Pressure Regulation: Limit Exceeded (Over boost Condition) Possible Symptoms Malfunction Indicator Light (MIL) ON Boost Pressure too high Reduced Power Output Possible Causes Hoses incorrectly connected, disconnected, blocked or leaking Boost Pressure Control Valve (N75) faulty Boost Pressure Sensor (G31) faulty Turbo Charger stuck/faulty Possible Solutions Check Charge Pressure Control System Perform Output Test (to check the Turbo Charger) Perform Basic Setting (to check the Charge Pressure Control) Perform Pressure Test to locate Leaks Check/Replace Boost Pressure Control Valve (N75) Check/Replace Boost Pressure Sensor (G31) Check/Replace Turbo Charger Now, if they are 2 unrelated problems, with the over boost, I've done some research and come up with some solutions. It would be great to see what you guys think... 1. Could try the 'Mr Muscle' technique to see if this helps (Un-Sticking Your TDi VNT Turbo Vanes.....). Would, if this worked, the veins clog back up again and the problem happen again? If so, over what time frame? 2. I've found a really good post that gives a couple of options as to what it could be, and said that on quite a lot of occasions turbos are replaced unnecessarily. See here > Diagnosing and Fixing Limp mode for A4 1.9TDI - TDIClub Forums But to summarise, it says it could be: Bad Maf (Oxygen Sensor) Leak in the vacuum system Faulty N75 Bad actuator Dirty gummed up turbo causing variable vanes to jam or stick What do you guys think to the above? 3. In another article I read (A3 TDI 140, HELP Overboosting, Limp Mode!) the chap had his turbo reconed but it still didn't work. He was then told it could be a problem with the EGR (blocked?) or Mass Air Flow sensor. A potential problem with the cylinder headwas also mentioned... Thoughts? So, to summarise, if anyone could rule out/elaborate on the above, it would a huge help. I am a novice, but learning all the time. So thank you! here are the key problems again... Car goes in to limp mode - Emission Control System light is on - code came up as P0234 (over boost) - car shudders when idle. Thank you! PS I have no warranty, would it be worth getting one!?