I saw this post yesterday and went by it because you mentioned that the problem was noticeable before you changed to a new faucet. It seems as if you are getting booted from this page and you have a legite problem going on here so I will give it a shot and shoot you to the top of the page again.
Check it by turning off the water service valve under the sink, removing the hot flex line from the water service stop. Run water into a bucket until it gets hot. Does it stay hot? Is it real hot? If yes then your problem most likely is in your faucet. If it does not get hot than the source of the problem is before the faucet. Maybe cold water mixing at the shower or a water heater that is not working properly.
If this is the only faucet that does not get hot, it could be that the shower valve is mixing cold water into the hot before it gets to the kitchen faucet, making the kitchen faucet luke warm at best. If this is the case, service the shower valve with a new cartridge.
The Local Plumber
Tustin, California http://www.TheLocalPlumber.com