Just got a 2003 audi a6 2.7 biturbo 6 speed with 134k+. I love the car but check engine light stays on so I cannot register it...car has already had all recall work done including ignition coil tsb and ECM reflash. Initial remedy since owning have replaced MAF sensor, changed all plugs and ignition coil associated with original misfiring cylinder, as well as replaced both valve cover gaskets hoping that would fix issue. CEL stayed on and have put roughly 200 miles on since. Got codes checked again and got p0171-system too lean bank 1,p0300,p0301,p0303-cylinder misfires and p491-air system insufficient flow bank 1. Am really looking for best direction from here...?thanks