Third time I have gotten codes p1127 and p1129. The first time I cleaned the mass airflow sensor. The codes were subdued for several months. The second time I replaced the mass airflow sensor. Codes were only subdued for a couple of weeks, but were, nonetheless, subdued. I got them again and I am clueless as too what is going on. The car has new vacuum lines, new air filter, and a new fuel filter. The car does stammer in an idle. Occasionally, I can start the car, shut it off, and restart it to get rid of the stammer. Any ideas about what is making this car run rich?