CEL help

Hi, I just picked up a 97 cobra, thought everything was fine until I went to get the emissions check I need for tags. I had a CEL, but it wasn't on in the dash, so i changed the bulb, had it reset, went back an failed the test again. codes p0171 an P0174 keep coming up they break out to lean engine back 1 and 2. I cleaned the mass air meter an it came back on again. I'm hoping its something simple. The car has a c&l meter, k&n filter an everything else under the hood looks stock. Looks like there are holes in the trunk from a nitrous bottle, if that matters. any help appreciated!