My 2000 GT was running decent, but stumbling occasionally so I replaced the plugs, a couple coil boots, fuel filter, and cam sensor (due to a code). It ran amazing right after, then upon the next start up has no power. It doesn't stall, but the rpms go from 1000 to about 400 back and forth idling. I had the alternator tested and it passed but with excessive ripple. The engine runs smooth, but is lacking power. No misfire or bucking, just feels like v6 power. I've also noticed the exhuast is not as loud. Should I be cleaning the MAF, replacing the alternator, or is it possibly something else?