There is only 1/2 supply coming in from the city. While doing some updating inside the house, we switch over to some 3/4 inch supply line. Could that in any way influence the pressure or flow at the fixtures at the end of the line? The wife thinks kitchen sink pressure has decreased.

There is only 1/2 supply coming in from the city Adding a 3/4" main to a 1/2 supply will neither add pressure or volume to your water, Your system can only put out what the supply puts into it. Regards, Tom

Most likely your water pressure/volume isn't the issue. More likely, is that the new faucet you installed has a restrictor installed in the aerator... required in all new faucets for years now!

Remove the aerator and se if that improves flow. If flow improves, you can try to remove the restrictor (a black or ring) from the aerator and see if that resolves your issue.

Let us know what you discover, OK?

Mark