I've had this problem for years and have learned to live with it, but today I got an idea to ask it here.
My kitchen sink has a problem where the water flows away from it slower than it flows into it. The first idea is, naturally, a clog, but I can swear that there is none. Checked the tubes myself. Also when the stream from the faucet hits the hole directly, it flows away mostly fine. However when it hits the edge of the hole, or doesn't hit at all, after a little while water will start gathering.
When it does, there is also a workaround - place your hand (or the plug) tightly over the hole, and the remove it upwards in a quick motion. In essence, you act like a little plunger and suck a bit of water back from the hole. After doing this once, the flow increases dramatically. A full sink empties in, like 10-20 seconds, with a loud, sucking noise. After it's empty, the water starts gathering again.
A long time a go I made some pictures to show in a local forum, but didn't get any satisfactory answers.
P.S. It'd be nice if someone could correct my terminology; DIY is not my area of expertise.