My Kohler Kitchen Fauset K-10412 Has slowed in water flow to about 40% of it's original flow, whether on cold or hot. Will the valve kit fix it? Should I replace any other parts?

Try to clean the Aerator first see if it will help, open the link below and see the image, Thanks.

John

Kohler Plumbing (http://www.kohlerserviceparts.kohler.com/ServicePartsPage.aspx?DocumentID=b88270fcf7464e44a 3228751fb5f371c&ModelID=8d01c5c06f5940a786abfabb95f36ea0)

It was simply the Aerator. I can't believe I forgot to check it. Thanks John.

Thanks for the update and am glad that we could help.

Regards,
John