I have a 99 X 5.0 AWD w/Auto - Everything is stock except K&N flat filter. For the last few months I've noticed that my battery voltage gauge will drop when multiple electronic items are running (i.e. - defroster, heater, stereo, headlights...) and the interior lights will dim. When this happens, it seems as though the truck loses some acceleration power and the idle becomes rough for a little while. I've had the battery checked, which it was determined to be okay. Would this be caused by a bad alternator or voltage regulator? What would be some symptoms of an alternator/voltage regulator going bad? I've had a problem with the X for a while (very poor gas mileage & horrible performance). The X runs like a POS, could this be attributed to a bad alternator/voltage regulator? I have done a search regarding this, but I am looking for some other symptoms that could be caused by a bad alternator/voltage regulator. Thanks for the any advice that is offered.