Welcome to the forum! Try using the "Search this forum" feature from the forum main page for keyword "P0171". You'll find that these codes have been addressed several times on this forum along with some good descriptions on how to check the PCV elbow, intake manifold, and comments regarding the DPFE. Since you have the code for both banks of cylinders the issue is likely to be something related to both banks such as the PCV elbow. An intake manifold/gasket would likely start out impacting only one bank.

The P0306 is a misfire code for cylinder #6. If it's been awhile since the spark plugs and wires have been changed the source of the P0171 and P0174 may have caused a plug to foul. Or you might also have a fuel injector that is not functioning properly contributing to the raw fuel smell.

If you plan to keep the vehicle for awhile you might start with a tune up (spark plugs, wires, fuel filter, air filter) since that is routine maintenance and could solve all three issues, but I suspect you'll still find yourself searching for the other issues addressed for P017x codes.

-Rod