Since I never posted what the problem was, I figured I should come back and tell all for the sake of those that find this with the search button.

My codes (P0505 and P0507) both completely went away after I fixed a boost leak. My intake manifold gaskets were blown, and I was leaking boost. Once I fixed that, the codes went away and never came back.

If you get these codes, be sure to check every point along the air intake path. Make sure that all your hoses are clamped, pipes sealed, and manifold gaskets are good.