Replace main shutoff valves going into the house, now have low water pressure in kitchen sink and hardly no water coming out of bathroom sink, except tub faucet flowing very well since the water heater is on the other side of the wall. Took all the screens and etc'd. Still nothing. Going crazy.

You have dirt inside the valves, need to remove the cartridges and flush out the dirt, please tell us the brand and the model of your valves, Thanks.

John

I agree with John. When you replaced that main debris broke loose. You may not have flushed the lines and now your valves are clogging. Try to answer John's question

In addition to John's advice: you may have dirt lodged in angle stops and water supplies as well. Also, some faucets have filter screens before cartridge. Furthermore, if you have very old galvanized pipes than you could clog the pipes anywhere in the house. Milo