Changed Faucet ... pressure lower

I recentlty changed the faucet in my guest bathroom with no problem. When i turned on the new faucet a decent amount of water came out but only about a third of the pressure as the old one. All connections are tight and valves are wide open. Water pressure everywhere else is fine.

Have you removed and cleaned any debris from the new faucet aerator?
That's usually the problem if there's a pressure issue after changing a faucet with an aerator.
Good Luck!
Mike

The aerator on the new faucet may be the Low-Flow water saving type where the old one if very old was not.

Many lav faucets now have a restricted flow.