Download 2003 Audi A4 Unstable Idle Service Manual – Customer Concern: Unstable Idle, Multiple codes P1136 Bank 1 Mixture adaptation Additive Range System To Lean P1297 Connection Charger to Throttle Valve Loss Of Pressure P0300, P0301, P0302, P0303, P0304 Misfire codes P1479 Brake Booster Vacuum Supply Malfunction Tests/ 1. Based on the codes set this problem is likely a vacuum leak and/ or damage to the turbo outlet side air boots. 2. Inspect all turbo ducting and boots for damage, looseness or leaks. 3. Inspect the breather/PCV system regulator valve at the top of the valve cover. The regulator valve prevent pressure build up in the crankcase under boost and has a manifold vacuum source to it. If the diaphragm ruptures in the regulator valve it will cause a large vacuum leak. Pinch off the vacuum source to the regulator valve and observe idle quality.