"tapping" sound when first started

What is your question?

My 3.5 sienna with 57000 miles started a tapping sound about 10000 miles back. During this winter, it has become much louder. This noise gets better after 3-4 miles driving, but is not "normal. I have changed the oil at least every 5000, using 5-30 synthetic. I took it to my local dealer, who's tech said it was carbon build up. He said he "blew it out on the road" and it quitened. The next morning, the noise was back and seems to be getting louder.