I have been having fuel trim problems which I believe is from poor voltage in my car affecting the MAF sensor (which I already replaced). I have a voltage meter as one of my gauges and it starts out on a cold morning at around 13.8, but it drops to around 13 as the engine heats up, or if it is a hot day. As a result, I have replaced all of the ground wires in the engine bay, ran an additional thick wire from the alternator to the battery, replaced the battery clamps, replaced the voltage meter in the alternator (and it needed it!), and replaced the battery with another good one that I had laying around, replaced the serpentine belt, tensioner pulley, idler pulley, and checked my fuses. I had NAPA test the battery and alternator and they said that it was working great (although maybe it was cold outside). I could simply replace the alternator but I wanted to ask you guys if there was anything I was missing before I threw down the money for it. I saw somewhere too about maybe the starter wires (going to battery and alternator) affecting it, although the car starts just fine.