The P0175 is an OBD-II diagnostic code that indicates your engine is running too rich. A "rich" engine mixture means there is too much air. Running an engine is more than simply feeding it fuel and oil. It is chemistry! Anyone familiar with stoichiometry knows that the ratio of fuel to air must be exact in order to cause an efficient reaction. Too much air can lead to carbonization of the pistons due to misfires. This would be considered A Bad Thing.

Possible causes include:

Vaccum failure is the most likely. Just check to make sure the vaccum hose is connected from air intake to the engine. Placement varies from engine to engine but it is normally near the exhaust manifold.

A mass air sensor would only get dirty if you use an oiled filter. Almost all filters today are made of paper and for single use. It gets dirty and you throw it out. K&G makes a reusable filter. It is not paper and by itself filters poorly. Oiling it creates a sticky surface for the particulate to attach to. They tend to filter better than simple paper filters, but are more expensive. Over time this oil can migrate to the MAF sensor. These sensors are very expensive, so I advise not using such a filter unless your vehicle's engine compartment isn't too confined.

The third cause may be that the air is fine but not enough fuel is getting in. A fuel line may need replaced, or even your fuel pump.

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