Sloan valves must be matched to the bowl.
You would be looking at a total replacement.
Something with a "pressure assist" if you are going that route.
Another option would be a "G-Max" Toto with the 3" flush valve.
If you have a "free" gravity toilet installed now, and it's not doing the job, you are most likely looking at replacement.

: any idea on how to do this or where to get sloan toilet valves in seattle? also do i need a new toilet?
: my "free" low flush toilet is driving me insane.