Now the toilet won't flush completely unless you hold down on the handle to let all the water out of the tank. The Fluidmaster had an adjustable cup - I replaced it with a regular one, and also tried one with the foam insert with no change. The toilet is an Eljer (I think), with the foam liner in the tank. Water level is set to the correct height - can't go higher with the fluidmaster design.
Anyone have any ideas? Customer is getting unhappy. Replace toilet?
Thanks for comments