The check engine light and service Stabilitrac lights / warnings came on. I had an engine code of P0171 and P0174. Checked the MAF (due to washing engine area with hose because of previous AC line failure and green dye covering everything), and cleaned it with MAF cleaner, Still had same problem, Had replaced the PCV valve, air filter and the MAF. Had checked all vacuum lines, intake manifold etc.. for vacuum leaks. was not able to find one. (thought MAF could be damaged due to previously mentioned water, apparently it was fine).

Engine was running rough, extremely hard downshifting, bucking. I did another search along motor area and found a vacuum nipple on the rear of the motor that had no cover on it. Looked it up, is not needed on my vehicle. Put a replacement cap on it and all the codes and service stabilitrac warnings went away instantly.

But it drove me crazy for 6 hours trying to figure out what was wrong.