Often times when you change out the supply tube on a bathroom sink faucet, you break loose calcium and mineral deposits inside of the piping system. (Calcium builds up over years of service). Since the calcium is rock hard, any movement of the piping system will cause parts of it to flake off and go out the end of the faucet.
Additionally, after 1992 faucets were made to conserve water, so the opening inside the spout is now reduced to only allow 1.6 gallons of flow. This reduction is generally due to a number of very small pinholes which can fill up with debris.
Removing the aerator at the end of the faucet and cleaning it out will generally solve this sink plumbing problem. Should you need additional help, Roto-Rooter has licensed plumbing specialists that can solve all of your plumbing problems. Call 1-800-GET-ROTO or schedule online.