Male lab not chewing

Question
I have a male lab approx 4 (was abandoned and I adopted 3 yrs ago).  He is my second lab - last one lived a great old age.  Problem - he is the most food driven lab I've ever met.  He is so motivated by food he will do anything.  He was on a diet (no people food and less dog food) and now is at ideal weight.  He is throwing up because he barely chews his food.  I have tried placing a rock in his bowl and he currently eats twice daily and each meal is broken down into 4 servings so he doesn't gobble as much.  He was eating a smaller kibble and not chewing at all so I have him on dental formula (huge kibble) and he still isn't chewing it!  He will vomit about 30 mins after eating.  Any other suggestions?  I've tried hand feeding every kibble but it still doesn't help as he swallows without chewing.  His desire to eat and gobble is uncontrollable with everything I've tried.

Please help.  I don't want him to have bloat.  He is a healthy dog other than this.

Thank you.

Answer
He sounds like a tough case even for a Lab.  The rocks in the dish is one of the standard techniques and usually works.  The large dental kibble sounded good too.  You could try the other technique of spreading it out on a cookie sheet, but I am not sure it would work either.  Another common trick is adding unsalted canned green beans or pumpkin to the food to fill him up.  I wonder how it would work to give them first, and then once he has something in his stomach, the kibble with the rocks or spread out.  

Some people claim adding water helps.  

Please let me know what you try, and how it works.