I have a 10 yr old Kohler, Finial (I believe) 1.5g flush toilet. Recently I noticed I could hear a trickle of water when it was idle so I replaced the fill valve and the flapper thinking it was one of the two. It still leaked into the bowl after I replaced those parts. I thought that it may be the overflow pipe, maybe the seat was worn or pitted, so I replaced it but it still slowly leaks. I'm out of parts to replace and ideas. Can someone help?
PS I used a Fluidmaster valve and a Moen overflow tube/flapper. The tube and flapper came as a kit. I since tried a Fluidmaster overflo/flapper kit with the same leaky result....