OK, now your description sounds like what ours were doing when they were ready for a faster flow nipple.

We've been using the Dr. Brown's bottles for several months and for a while we used an Evenflo nipple instead of the Dr. Brown's nipple because the flow was in between the Dr. Brown's level 2 and 3. I'd do that instead of messing with the other nipple.

Also, you might try the level 2 for more than just a few minutes before deciding if it's really working. It'll take a few feedings for your son to get used to it. You could always pace him so he doesn't choke. If you haven't had to do that before (we had to in the NICU when they first started on bottles), you hold the bottle just tipped enough so the nipple is full of milk and tip the bottle down after every couple swallows to give him a chance to catch his breath and swallow if he needs to.

Mom to GBG born in July 2009 at 30w6d: 3#10oz, 3#12oz, 3#2oz