Fellow Audians, I have a couple of questions; 1. How can you isolate a faulty fuel injector? 2. How do you know if your cold start valve is bad? My symptoms are; 1. Hesitating startup. 2. Carbon fouled plugs 3. Heavy black soot build-up on exhaust If anyone can steer me in the right direction please do, before I begin to dump a lot of cash on parts that I don't need. Thanks Mark 90 200T