getting tri-fecta of CEL codes and looking for some direction

Hi Everyone,



Thanks to this site I have been able to save myself some serious $ and I thank all of you for sharing!



I am now running into an set of error codes on my wifes ride that I feel like i might be chasing my tail a little bit.



2008 A4 2.0L Quattro (b7)



throwing a 2181, 0455 & 0171



Dealer replaced fuel filter and said it would be another $500 buck to swap out the CTS (coolant temp sensor).... HA.



I swapped out the CTS for $23 and 1/2 Hour :)

Coolant level is Right at the Max line...

only other thing for the 2181 I can find is swap out the thermostat; even thought it isn't overheating and haven't noticed anything odd...



I don't have vac testing equipment and can't hear any obvious leak... thought about replacing the gas cap just to make sure it is sealing right and to rule it out.



Anyone run into these before to gimme some direction... not sure what to try next if with out just throwing $ at it