Hey guys I have an issue with my A4 that I have put off too long. Last January my car started misfiring.. was shuttering when sitting in idle for about a minute or more. I noticed a big power loss and fuel economy went down. Pulled codes.. there was a misfire detected in all four cylinders and a turbo underboost so figured it was something centralized. I replaced all coils and plugs, and that didn't fix it. It also leaks oil and coolant and wasn't sure if it could be a head gasket going. If anyone could help that would be great!