Kitten who is always EXTREMELY hungry?

I rescued Turbo from a shelter near us back towards the end of May (the 27th, to be exact), and he was extremely skinny; you know how they inject microchips into the general area of their scruff/shoulder blades?  Well, you could feel Turbo's  Anyhow, at the time of adoption, he was supposedly 8 weeks, although I really do believe he was younger.  When we first brought him home, we had 3 cats (another was a rescue, Cam, the other was our 2-year-old Maine Coon mix, Grizzly), so I would always split them up when it was feeding time - Turbo shut in the bathroom, Grizz in the walk-in closet, Cam in the bedroom, and everyone was happy.  However, whenever I would try to leave doors open, Turbo would DART from his bowl and inhale everyone else's food!  During the first week, he was actually food aggressive (a food aggressive itty bitty kitten...very funny to watch, I might add) towards our 85-lb Doberman and either of the cats who would dare venture near him.  Turbo will climb up onto the counter tops and lick off dishes (ketchup, mayo, pasta, any scrap that is left out is his for the taking); he even picked potatoes out of a boiling beef stew that I was making and pridefully drug them onto the floor, where he devoured them the best he could with his little baby teeth.  I figured this was just a phase - he hadn't seen much food, let alone good food, while he was at the shelter and for who knows how long before, so I figured his body was just playing catch-up.  In addition, I also thought he might have had worms (his little tummy looked quite bloated for a week or two), however that has passed and I have seen nothing in his feces. However, after having him in our home for about a month and a half, his pigginess is still persisting and it baffles me!  I still split everyone up during feeding time, which works well so long as I make sure to put up everyone else's leftovers before letting Turbo the tubby out.  He still figures out ways to get scraps off the counter tops (nothing is safe!), camps out in the sink for dirty dishes, and will LAUNCH himself into the dishwasher at any chance he gets!  I typically put the food (which is in a pretty sturdy bag with a ziploc at the top) up on a shelf in our closet...some place I almost knew he would never be able to reach, just to find that he had somehow gotten up there and gnawed up the bag until he could get inside and eat to his little heart's content.

Now here is my main question:  is this shear pigginess or is it a cause for concern?  His diet as of right now consists of just dry food (although I do plan to begin adding a can of wet food/day)...I am feeding him about 1/2 cup/day of grain-free, high-quality food.  With Grizzly (who we have had since 8 weeks), I would just fill up a huge Tupperware and leave it out and he would pace himself...with Turbo, when I tried that, he made himself sick.  Whenever he zooms around and gobbles up everyone else's food, he often becomes sick afterwards and his tummy looks as though it might pop.  Any opinions or feedback on this?

I do think that given his background, he is definitely food aggressive. However, I also think his food might not be satisfying him. Dry food by nature has a lot of carbs (even grain-free ones). What growing kittens need are high animal protein and fat. Those are actually the things that make cats feel satiated. Empty carbs that cats don't have a nutritional need for are probably not satisfying him. I would adding as much of a high animal protein/fat/low to no carb wet food to his diet as you can and see if his behavior changes. To learn more about feline nutrition, please visit www.catinfo.org. Written by a vet, it also provides a comparison chart of common cat foods broken down by protein/fat/carbs.

Also how often are you feeding him? At his age, smaller, more frequent meals will work better.

Thanks for the reply and great info! I feed him twice daily, but he also gets into other food just about constantly (yet still inhales his food at feeding times).  I think I may try to give him a can of food sporadically throughout the day in addition to his regular dry feedings (perhaps cut this amount back a tad) and see if that helps to satisfy him.  Thanks again!

I agree with vball91:  I would try feeding your kitten more wet food, less dry food; and more frequent, but smaller meals.  Carbs don't satisfy cats like protein does; cats need (versus "want") more fat than humans.

And, watch his weight:  I'm not concerned about him getting fat, but if he maintains or looses weight, that is a cause for concern (and vet visit).