08 S6 misfires.....P0171 code

[cellosven]

Can I remove air filter and detach air flow sensor momentarily to eliminate air flow sensor as a problem?
Thanks,

[haloguy628]

Check the vacuum hoses. Usually lean condition means there is leak in the vacuum system.

The first I would check is not actually a hose but a plastic tube located behind the removable plastic cover with the Audi rings on it. It's right above the oil filter close to the firawall. That plastic tube can easily crack or break if one is not careful changing the oil filter because the electric harness and the vacuum tube has to be moved out of the way to get to the oil filter.

I would worry about the MAF's as last resort. If MAF was bad you would have misfires and fluctuating idle. I would clean both MAFs with electronic cleaner. Spray the cleaner on the blade and gently use Q-tip to clean. Spray the connectors too.

[Nizmo]

The intake manifold gaskets do leak, as well as the IM flaps breaking.

Personally, I wouldn't pull 2 MAF's on a master slave system.