99' v8 5.0 Chatter Noise

Has 141,000 miles on it (all highway). When I accelerate I hear a very fast, but not loud, chatter that varies on how fast I accelerate. At idle and when my speed is constant I do not hear the noise (it goes away when I ease off the accelerator). I do not notice any difference in performance from before. Could this be just a leak in the exhaust, or maybe a sign that something is going bad, like the alternator?

Try using some octane booster or injector cleaner ($2 to $5, I got the higher end). I allowed mine to go almost empty in the heat of the summer, then got 5 gal of bad low octance gas to make it to a reputable station. Clatter was AWFUL! got a tank of med grade and added the booster, haven't had a problem since. I try to use high octane cuz of 127K miles, but in cooler weather, good medium grad works great.