Right now I constantly have a P0171 code, System Too Lean (Bank 1). I cleaned the MAF a few days ago, and that did not fix the problem.

However, I did notice while cleaning the MAF, that the seal at the connection between the air-box and the pipe that goes to the throttle body is bent, and probably letting air in. Could this be a cause for the trouble code?

I also notice a lack of power in 1st gear, and a hesitation in other gears while accelerating.

 

that's actually one of the main reasons why you would throw that code, so i'd say that's the cause. I would get that fixed, should take care of your problems.